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Copyright N°__ 


COPYRIGHT DEPOSIT 


































A 


MANUAL OF ASSAYING: 


THE FIRE ASSAY OF GOLD , SILVER, AND 
LEAD , INCLUDING AMALGAMATION 
AND CHLORINATION TESTS. 


BY 

ALFRED STANLEY MILLER, 

* I 

Professor of Mining and Metallurgy , 
University of Idaho. 


SECOND EDITION REVISED AND ENLARGED. 


FIRST THOUSAND. 


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JOHN WILEY & SONS. 


London: CHAPMAN & HALL, Limited. 

1901. 





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MAR 26 "1902 

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BY 

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PREFACE. 


The plan of this book is a departure from 
the books on this subject with which the 
writer is familiar. The apparatus is brought 
in where its use is easily understood. The 
student is taught the operations of the tire- 
assay by practising with an ore easy to 
assay. He is then better prepared to under¬ 
stand the directions for assaying more com¬ 
plex ores. 

The writer’s experience in teaching this 
subject has convinced him that there is room 
for a book of this kind. 

The following books have been consulted 
in the preparation of this book: 



IV 


PREFACE. 


Aaron’s Assaying; Ricketts and Miller’s 
Notes on Assaying; Hiorns’s Practical Met¬ 
allurgy and Assaying; Furman’s Manual 
of Assaying ; Brown’s Manual of Assaying; 
Beringer’s Assaying; and Rose’s Metallurgy 
of Gold. 

The crucible charges from Ricketts and 
Miller’s Notes on Assaying, and the crucible 
and scorification charges from Furman’s 
Manual of Practical Assaying are quoted by 
permission of the authors. 


Juue, 1900. 


PREFACE TO THE SECOND EDITION. 


In this edition the chapter on slags has 
been enlarged, and the following subjects 
have been added : The assay of ore con¬ 
taining coarse metal, the assay of copper 
ores and copper-bearing materials for gold 
and silver, the dry assay of mercury, the 
cyanide method and the iodide method for 
the determination of copper, and the ammo¬ 
nium molybdate method for the determina¬ 
tion of lead. 


Moscow, Idaho, March, 1901. 





CONTENTS. 


CHAPTER I. 

PAGE 

Cupels and Flux. 1 

CHAPTER II. 

Assay of Ores. 5 

CHAPTER III. 

Notes on the Assay of Ores... 29 

CHAPTER IY. 

Fluxes and Reagents. 47 

CHAPTER Y. 

Slags.. 55 

CHAPTER YI. 

The Assay of So-called Refractory Ores . 61 

CHAPTER YII. 

Amalgamation and Chlorination Tests. 82 

vii 










Till 


CONTENTS. 


CHAPTER VIII. 

PAGE 

The Assay of Ore containing Coarse Metal. 88 

CHAPTER IX. 

The Assay of Copper Ores and Copper-bearing Materials 
for Gold and Silver. 91 

CHAPTER X. 

The Dry Assay of Mercury. 100 

CHAPTER XI. 

Volumetric Determination of Copper. 108 

CHAPTER XII. 

Volumetric Determination of Lead. 124 

APPENDIX A. 

Supplementary Notes on the Assay of Ores. 128 

APPENDIX B. 

Tables . 136 









A MANUAL OF ASSAYING. 


CHAPTER I. 

CUPELS AND FLUX. 

1. To Make Cupels. 

Take a miner’s pan (Fig. 1) full of bone- 
ashes and pass them through a 40-mesh sieve, 
moisten sufficiently to make them cohere 



Fig. 1. 

slightly, like flour when compressed in the 
hand (about 1 oz. of water to a pound of 
bone-ashes). Work them between the hands 
until the moisture is evenly distributed. 








2 


A MANUAL OF ASSAYING. 


Place a l|-inch cupel mould (Fig. 2) on a 
smooth iron plate or anvil, till it with the 
moistened bone-ashes, and drive the die down 
by a number of light blows with a mallet 
(Fig. 3), turning the die after each blow. 



Fig. 2. 



Fig. 


8 . 


Move the mould on the iron plate so as to 
give the cupel an even base, then turn the 
mould and die upside down, and push the 
cupel out with the die. Turn cupel when 
taking it off. Place the cupels on a dry 
board, and dry them slowly and carefully in 


a warm room. 











































CUPELS AND FLUX. 


3 


Too much water makes the cupels less 
porous, and if too little water is used, they 
will crumble. If the cupels stick in the 
mould, the bone-ashes are too dry or they 
are compressed too hard. Cupels should be 
made several weeks before they are used. At 
the Royal Mint the cupels are made two 
years before they are used. 

2. Flux for Ordinary Silicious (Quartz) Gold and 

Silver Ores. 

Litharge, PbO.100 parts 

Bicarbonate of sodium, HNaC0 3 . .100 u 
Wheat Hour. 4 “ 

Spread a rubber or an oil cloth on the mix¬ 
ing-table. Weigh out 5 lbs. litharge, PbO; 
5 lbs. bicarbonate of sodium, HNaC0 3 ; and 
31 ozs. wheat hour, and pass them through 
a 40-mesh sieve, on the cloth. Spread the 
mixture out evenly, then, by lifting a corner 
of the cloth and drawing it forward, roll the 
mixture on itself, then take another corner in 




4 


A MANUAL Oh ASSAYING. 


the same way ; occasionally spread out the 
mixture and proceed as before until it is 
thoroughly mixed. Place the mixture in a 
box for future use. 


CHAPTER II. 


ASSAY OF OKES. 

3. To Prepare the Sample of Ore. 

Take several pounds of rich silicious 
(4 artz) ore, free from sulphur, arsenic, anti¬ 
mony, etc, break the large pieces by a 
hammer, then in an iron mortar (F ig. 4), so 



Fig. 4. 


that the largest pieces are not over about an 
inch through the longest diameter, then pass 
the ore through the crusher (Fig. 5), then 
shovel the ore on the tin sampler (Fig. 6 ), 




6 A MANUAL OF ASSAYING. 

1 

where half is caught and half passes through, 



Fig. 6. 

repeating until the sample is reduced to 
about a pound. Now pass it through the 











































































ASSA Y OF ORES. 


7 


crushing rolls, and pulverize it on a bucking- 
board (Fig. 7) until it passes an 80-mesli 
sieve (some use a 100-mesh). 



In conducting the operation on the buck¬ 
ing-board, place your left hand on the niuller 
and grasp the handle with the right hand; 
throw your weight on the muller and move 
it back and forth, raising the handle when 
drawing toward you, and depressing it when 
p u sh i ng back ward. * 

*Ores can bo pulverized in the iron mortar alone, or by 
other apparatus than is mentioned here. 

Everything used in these operations must be perfectly 
clean. Particles of rich ore left from the last sample in the 
iron mortar, in the crusher, on the bucking-board, in the 

































8 


A MANUAL OF ASSAYING. 


After passing the ore through ail 80-mesh 
sieve, mix it thoroughly on a rubber or an 
oil cloth. Spread the ore out evenly on the 
cloth, lift a corner of the cloth and draw it 
forward, rolling the ore on itself (merely 
sliding the ore on the cloth does not mix it), 
and proceed as directed for mixing flux 
(under 2), and put the sample into an ore- 



pan (Fig. 8). Read the notes on ore-sam¬ 
pling and ore samples on page 29. 

4. Assay Ton Weights. 

The ore is weighed by Avoirdupois, and 
the gold and silver by Troy weight. The 

sieve, in the cleaning-brush, or on the mixing-cloth, care¬ 
lessness or uncleanliness in any of the operations or about 
the laboratory, make the results unreliable; and unless a 
person is strictly honest and is determined to do accurate 
work, he should not engage in this line of work. 

After pulverizing rich ore, clean the apparatus with 
barren quartz or glass. 








ASSAY OF ORES. 


9 


system of assay ton weights is very con¬ 
venient and easily understood. 

«/ 

1 lb. Avoirdupois = 7000 Troy grains. 

2000 lbs. = 1 ton. 

2000 X 7000= 14,000,000 Troy grains in 
1 ton Avoirdupois. 

480 Troy grains = 1 oz. Troy. 

14,000,000 -f- 480 = 29,166 + Troy ozs. in 
2000 lbs. Avoirdupois. 

By taking as many milligrams of ore as 
a ton contains ounces, every milligram of 
gold or silver extracted is equivalent to an 
ounce to the ton. In one assay ton (A. T.) 
there are 29,166-4- milligrams. Hence by 
taking one assay ton of ore, 1 milligram of 
gold or silver extracted = 1 oz. Troy to the 
ton of ore. 2000 lbs. : 1 A. T. :: 1 oz. 
Troy : 1 milligram. Weighing by grains, 
the assay ton contains 29,166+ grains, hence 
1 grain of gold or silver extracted = 1 oz. Troy 
to the ton of ore. 


10 


MANUAL OF ASSAYING. 


5. To Make the Assay. 

Weigh an assay ton of the sample, pre¬ 
pared as directed under 3, on one of the pulp- 
balances* (Figs. 9 and 1 ( >), taking a little 



with the pulp-spoon (Fig. 11) from all parts 
of the sample.f Take about 85 grams, or 04 
c.c., of the flux (Chap. I, 2), and mix the ore 
and flux in the same manner as directed for 

* Put the assay toil weight on the left-hand pan. 

t A better method is to spread out the mixed ore in a 
thin layer, then take the sample, with a steel spatula hav¬ 
ing a square end, from all parts of the layer, driving the 
spatula to the bottom of the layer each time. This should 
be done gently, taking care not to jar the ore. 


































ASS A Y OF ORES. 


11 


mixing sample (under 3), then pour it into a 
20-grm. clay crucible (Fig. 12), in which 



riu. j-jl. 

about 10 milligrams of 0. P. silver has pre¬ 
viously been placed. Weigh out another assay 
ton of the ore and proceed as before, omitting 




























































12 


A MANUAL OF ASSAYING. 


the silver.* Cover the charge in eacli crucible 
with about 15 grams of unfused powdered 
borax. Consider the charge in the crucible 
containing the silver No. 1, and the other 
No. 2. Place No. 1 on the left in the cru- 



Fig. 13 . 


cible-furnace f (Pig- 13), and No. 2 on the 
right. You will know them by these posi¬ 
tions through all the operations. 

* When assaying for gold only, add silver to both charges. 
When the approximate amount of gold in the ore is known, 
add an amount of silver to insure separation (see 8). 

t If a gas-furnace is used, the crucibles may be put into 
the furnace before the fire is started. If a coke- or a coal- 
furnace is used, the fuel should be red hot and in such a 
condition, before the crucibles are put into the furnace, that 
the heat can be raised gradually. Make a nest in the glow¬ 
ing coals for the crucible, and pack the fuel around the cru¬ 
cible. Or put an old crucible into the fuel, and put the cru- 



































ASSAY OF ORES. 


13 


6. Fusion in the Crucible. 

Fuse the charge, keeping the fire hot 
enough to keep the charge liquid. When the 
charge has subsided and is in a state of quiet 
fusion (the chemical reactions having all 
taken place, the charge may still have a con- 



Ftg. 14. 


veetion motion), urge the fire and after a few 
minutes remove the crucibles, one after an¬ 
other, from the tire, with the crucible-tonu's 
(Fig. 14), give the crucible a circular, swing¬ 
ing movement, to wash the sides of the cru¬ 
cible, tap it on the floor or table to settle the 

cible with the charge in its place, when the fire is in the 
proper condition. If, after the charge melts, the heat is 
checked sufficiently to stop the action, the assay is said to 
“freeze.” In this case the assay is defective, and a new 
assay must be made. 

Crucibles with the charges should be gently heated, before 
they are put into a hot fire, to prevent the crucibles from 
breaking, and to prevent “blowing” (see under sodium 
bicarbonate on page 48). 



14 


A MANUAL OF ASSAYING. 


lead, and pour the liquid contents, at first 
slowly, then rapidly, into a mould (Fig. 15), 
which has previously been warmed. 



Fig. 15. 


w hen the assay has partly cooled, turn it 
out of the mould. The slag should be evenly 
colored, and should contain no globules of 
lead. Break the slag by a hammer (Fig. 16) 



on an anvil (Fig. 17), hammer the lead 
button to a cube, flatten the corners, brush it 
(Fig. 18), and place it in its proper place on 
the button-tn iy (Fig. 19). 




















.4&SJF OF ORES. 


15 



Fig. 17. 



Fig. 18. 



Fig. 19. 
































































































































































































































































































































































































16 


A MANUAL OF ASSAYING 



Combination Furnace. 




















































































































































































































































ASSAY OF ORES. 


17 


7. Cupellation. 

Place cupels (two more than the number 
of buttons) in the muffle of the muffle-furnace 
(Fig. 20), in the same relative positions that 
the crucibles occupied in the crucible-furnace. 
A little bone-ash should be sprinkled on the 
floor of the muffle. 

When the cupels are at a red heat, and the 
muffle at a bright orange-red,* charge in the 
buttons by the cupel-tongs (Fig. 21), and 
close the muffle until the black crust has 
disappeared from the melted buttons, then 
open the muffle. The lead oxidizes, and, to¬ 
gether with the oxides of other metals, is 

* An idea of the approximate temperature in the muffle 
can be gained by Pouillet’s scale of temperatures : 



Deg. c. 

Deg. F. 

Incipient redness. 

. 525 

977 

Dull red. . . 

. 700 

1,292 

Cherry-red... .. 

. 900 

1,652 

I )eep orange. 

.1,100 

2,012 

White. 

. 1,300 

2,372 

Dazzling white. 

. 1,500 

2,732 


Foot-note continued on page 18. 










18 


A MANUAL OF ASSAYING 


absorbed by the cupel. When nearly all the 
lead has been oxidized, moving rainbow- 

The direction of the fumes serves as a rough indicator of 
the temperature: 





Eight. 




































ASSAY OF ORES. 


19 


colored rings appear on the button, after 
which the button becomes duller, and the 


Fig. 21. 

cupellation is finished. If the button is less 
than one-third gold, it should be cooled 
slowly by bringing it to the front part of the 
muffle until the button begins to solidify, then 
moving it back to the hotter part of the 
muffle for a while, or by placing a red hot 
cupel over it, as it absorbs oxygen when 
molten and gives it out suddenly on solidify¬ 
ing, from which loss may result from “ spit¬ 
ting.” 



Remove the cupels from the muffle, plac¬ 
ing them on a tray (Fig. 22) in their proper 





20 


A MANUAL OF ASSAYING 


positions. When the buttons have partially 
cooled, remove No. 2 from the cupel by means 



Fig. 25. 

of a pair of pliers (Fig. 23), squeeze it to 
loosen the adhering bone-ash, and brush it 








































































































































ASSA Y OF ORES. 


21 


with the assay-button brush (Fig. 24), place 
it on the left-hand pan of the button-balance 
(Fig. 25), and weigh it. 

8. Parting. 

After noting the weight of the button, fuse 
it with sufficient silver to make the silver 
about 2| times that of the gold,* lay it on an 
anvil and flatten it by a few blows of a ham¬ 
mer. Pour nitric acid, 1.16 sp. gr. (21° 
Baiirne) into a test-tube (Fig. 26) to the 
depth of a little over the diameter of the test- 
tube, warm the acid, and then put the bead 
into it, and boil it until the acid becomes 
colorless. After all fine particles have settled, 
pour off the acid and boil again with the 
same amount of acid of 1.26 sp. gr. (32° 
Baume). Pour off the acid, fill up the test- 
tube with distilled water, and after the gold 
has settled, pour off the water, fill the 


* This is called “ inquartation.” 



22 


A MANUAL OF ASSAYING. 


test-tube again with water, invert an anneal¬ 
ing-cup (Fig. 27) over the mouth of the test- 
tube, and, by a quick movement, invert the 
test-tube, keeping the cup over the mouth of 
the test-tube, and till the cup with water. 
The gold settles into the cup. liaise the 




Fig. 26. 


Fig. 27. 


test-tube a little at a time until it is nearly 
even with the top of the annealing-cup (this 
should be done over a sink), then (after the 
gold has settled) quickly remove the test- 
tube, and after the water has run out, hold it 
to the top of the cup (using it as a pouring- 
rod) and pour the water out of the cup. 
With the last drop, by tapping the cup, bring 
all the a'old loo-ether in the bottom of the 

o O 















ASS A Y OF ORES. 


23 


cup. Heat the cup to redness, and put it 
on the tray (Fig. 28) in its proper place. 
Do tlie same with the button, No. 1, (ex¬ 
cept that this button may need no additional 
silver). When cool, weigh No. 2. The dif¬ 
ference between the weight of the button and 
the weight of the gold is the weight of the 



Fig. 28. 


silver. Weigh the gold of No. 1, which 
should closely agree with the weight of No. 2. 

Dead the notes on Fusion in the Crucible 
and on Cupellation on pages 32 and 34, and 
repeat the assay until you can make dupli¬ 
cate assays (duplicates by adding the same 
amount of silver, and duplicates without 
adding silver) that agree. Then practise on 
low grade ores of similar character. 











































24 


A MANUAL OF ASSAYING. 


9. Scorification Assay. 

From the sample of ore prepared for the 
crucible assay (under 3), take ^ assay ton 
(A. T.), weigh out \\ A. T. of C. P. gran¬ 
ulated lead, mix about half of the lead with 
the ore, put the mixture into a scorifier (Fig. 
29), smooth it down, mix the remaining lead 



Fig. 29. 


on the cloth or papfcr on which the ore and 
lead were mixed, so as to take up any par¬ 
ticles of ore that may have been left on the 
mixing-cloth, spread it over the mixture 
evenly, and put about 0. 20 grams of borax 
glass on top. Add a little silver to this, and 
make a duplicate, omitting the silver.* 

The scorification assay is made in the muf¬ 
fle, which should have a temperature of 1050° 
to 1100° C. When the muffle has reached 


* When assaying for gold only, add silver to both charges. 






ASSAY OF ORES. 


25 


the required temperature, charge in the scori- 
fiers * by the scorifier-tongs (Fig. 30), in the 



under 5. Close the muffle until fusion takes 
place, then open it. A ring of slag soon 



Fig. 30. 


forms which is increased by the addition of 
the lead oxide which forms, and in about 30 
or 40 minutes, it closes over the metals. 
When the slag has closed over the metals, 
place, by the cupel-tongs, about 0.2 gram of 
powdered charcoal, wrapped in tissue-paper, 
on the surface of the slag, and close the 
muffle. This reduces some of the lead oxide, 
and the globules of lead fall through the 
slag and carry the gold and silver down, 
which had remained in the slag. When the 

* Scorifiers should be dry, and should be warmed with 
the charge by placing them on the furnace for some time 
before charging them into the muffle, to prevent them from 
breaking. 











26 


A MANUAL OF ASSA YING. 


fusion becomes quiet, pour it into a mould. 
The lead buttons are-treated in the same 
manner as already explained under the cruci¬ 
ble assay. 

Read the notes on the Scoritication Assay 
on page 43, and repeat the assay until you 
can make duplicate assays (duplicates by add¬ 
ing the same amount of silver, and duplicates 
without adding silver) that agree. 

10. Lead Flux. 

A mixture of 

Bicarbonate of sodium, NaIIC0 3 . 16 parts 
Carbonate of potassium, K CO .. ... 16 “ 


Borax glass. 8 “ 

Wheat flour. 4 u 


11. Fire Assay for Lead. 

Prepare a sample of galena (lead sulphide) 
ore as directed under 3. Weigh out 5 
grams of the ore, and mix it with 18 
to 20 grams of lead flux, pour it into a 




ASS A Y OF ORES. 


27 



dry fine common salt * to the depth of about 


i inch, and stick 3 8-penny nails into the 
charge. Make a duplicate assay. 


Make this assay in the muffle, which should 
be at a cherry-red heat before the crucibles f 
are charged in. After the crucibles are in. 
troduced into the muffle, close the muffle 



Fig. 31. 


Fig. 31 a . 


and, in about 20 minutes, raise the heat. In 
30 to 40 minutes the assay will be in a. state 
of quiet fusion ; then take out the crucible and 
remove the nails J with a pair of small tongs 

* Mix the salt on the cloth on which the ore and flux were 
mixed, so as to take up any particles of ore that may have 
remained on the cloth. 

t See last paragraph of footnote on page 13. 

I Another method is to seize the nails, above the slag, 
with a pair of straight tongs, and throw the lead off the 
nails by tapping the tongs on the top of the crucible. The 
same method should be used when nails are used in the 
assay for gold and silver (see page G5j. 






28 


A MANUAL OF ASSAYING. 


(Fig. 31a) ; after washing them in the slag, 
and tapping them on the inside of the crucible 
to remove adhering particles of lead, tap 
the crucible on the floor, and pour the assay 
into a mould. After cooling, hammer the 
slag off, flatten out the lead button and 
weigli it. 

Example .—If the lead button weighs 3 
grins., 3.00 5 (the amount of ore taken) = 

00 per cent of lead; 00 per cent of 2000 
lbs. = 1200 lbs. lead in a ton of ore. When 
lead is worth 4 cents a pound, 1200 lbs. are 
worth 1200 x $-04 = $48.00. 


CHAPTER III. 


NOTES ON THE ASSAY OF ORES. 

12. Notes on Ore-sampling and Ore Samples. 

1. Large samples of ore should be crushed 
to a size not much larger than J inch, mixed 
on a cloth, spread out evenly, and divided 
into quarters. Remove two opposite quar¬ 
ters, mix the other two thoroughly, spread 
out, and quarter as before. Repeat this until 
the sample is reduced to the required size. 
After the sample is reduced to 2 or 3 lbs., it 

should be crushed finer before reducing it to 
a smaller sample. 

Sampling can also be done by channelling , 

which consists in spreading the mixed ore out 

in a square, taking out samples in parallel 

grooves across the square, as far apart as the 

29 


30 


A MANUAL OF ASSAYING. 


width of the channels, then at right angles to 
these channels; or by a sampling tin, quarter- 
ing-shovel, split shovel, or mechanical sam¬ 
pler. 

2. Before pulverizing, damp samples must 
be dried on a water-bath (Fig. 32), or in a 
drying oven (Fig. 33) at a temperature not 
above 100° C. 



3. After the sample is thoroughly mixed, 
pour it into an ore-pan. Mark the number 
of the sample, the character of the ore, and 
other data on a piece of paper or cardboard 
and put it into the pan with the ore. 

4. Do not shake, tap, or otherwise disturb 











































NOTES ON TTIE ASSAY OF ORES. 


31 


the sample before weighing out the amount 
of ore for assay. If the ore is not immedi¬ 
ately weighed out, the sample must be mixed 
asrain before wemhhm out the ore for assay. 

O O O J 

By standing, the heavy particles have a ten¬ 
dency to settle to the bottom of the pan on 
account of their weight, aided by the vibra¬ 
tions of the building, produced by various 
causes. 

5. All the ore should pass the sieve. If 
scales of gold are left on the sieve, put them 
on the bucking-board, cover them with part 
of the tine ore and grind hard. Repeat until 
tliev pass the sieve. If the scales cannot be 
pulverized, weigh the sample that passes the 
sieve, and the scales separately, cupel the 
scales with a little lead-foil, and calculate the 
value per ton of ore, to which add the 
value of the assay of the ore that passed the 
sieve. 

For methods of assaying ores and materials 
containing scales of gold, or other coarse 


A MANUAL OF ASSAYING. 


32 

metal, and for a method for calculating the 
value of such ores, see Chapter VIII. 

13. Notes on Fusion in the Crucible. 

1. The ore and flux must be intimately 
mixed, so that as the lead is reduced it can 
come in contact with the gold freed by the 
pulverization, and by the fusion of the ore. 

2. The object of the fusion is to collect 
the gold and silver in a button of lead, re¬ 
duced from the litharge, and to form a fusible 
slag with the fluxes and gangue of the ore. 

3. Crucibles should not be over three- 
fourths full, and less in case of sulphide ores. 

4. The assay swells when heated ; prevent 
it from boiling over. 

5. Causes of boiling over: («), too much 
borax, especially in oxidized ore; (7>), too 
much soda; (c), unfused borax mixed with 
the charge; (J), rapidly heating a charge 
containing nitre. 

6. Boiling over can be prevented by re- 


NOTES ON THE A88A Y OF OURS. 


33 


moving the cover, if covered, checking the 
heat, or by throwing a teaspoonful of salt 
into the crucible. 

7. If the slag is pasty, add borax. If 
accuracy is required, make another assay, 
fluxed as indicated by the first assay. The 
fluxing of other than silicious ores will be 
explained when they are taken up. 

8. After pouring, examine the crucible. 
If the crucible contains shots of lead or pasty 
masses, the assay is defective. 

9. The fusion can be made in a muffle; the 
temperature should be about the same as in 
the scorification assay. When the fusion is 
made in the muffle, \ an assay ton of ore is 
usually taken, and fluxes in the same pro¬ 
portion. 

For convenience and economy, where many 
assays are made, use a soft-coal furnace con¬ 
taining two large muffles, one above the 
other. The fusion can be made in the lower 


34 


A MANUAL OF ASSAYING. 


muffle wliile cupellatiou is going on in the 
upper muffle. 

14. Notes on Cupellation. 

1. The cupel should be about one-half 
heavier than the button. 

2. Spirting of the lead button sometimes 
happens when there is too strong a draught, 
or when the button contains volatile elements 
as arsenic, antimony, sulphur, carbon, bis¬ 
muth, or mercury. Examine the cupel for 
small beads of metal. 

3. When the muffle is not hot enough, put 
a piece of charcoal in the front of the muffle, 
which will raise the temperature. Some also 
use this to equalize the temperature in the 
muffle, as the front of the muffle has always a 
lower temperature. The temperature in¬ 
creases from the front to the back of the 
muffle. 

4. After the cupellation is finished, the 
button should be left in the muffle a few 


NOTES ON THE ASSAY OF ORES. 


35 


minutes to remove all remaining traces of 
lead. 

5. When the button begins to solidify, it 
“ flashes,” suddenly “ brightens/ 1 which is due 
to the sudden disengagement of the latent 
heat of fusion. 

0. Buttons containing a large proportion 
of silver will “spit,” if cooled rapidly. This 
“spitting,” “sprouting,” or “ vegetation,” as 
it is called, may be prevented in three ways : 
(a), by drawing the cupel to the front of the 
muffle to partly cool the cupel, and when the 
button begins to solidify, pushing it back to 
the hotter part of the muffle where the out¬ 
side of the button melts, and the solidifica¬ 
tion goes on from below ; (/>), by inverting a 
red hot cupel over the cupel and button ; (c), 
by closing the muffle, withdrawing the fire, 
and allowing slow cooling to go on. The 
“ spitting ” is due to the absorbing of oxygen 
by the silver when molten, and giving it out 
suddenly when solidifying. 


36 


A MANUAL OF ASS A TING. 


7. Silver is volatile at a high temperature, 
also gold, to some extent. Silver begins to 
volatilize at a white heat. 

A strong draught of air cools the cupel, 
and prevents the oxides from being absorbed 
as fast as formed. 

The longer the time required for cupella- 
tion, the more the loss by volatilization and 
absorption by the cupel. 

Some assayers keep the mlithe at a low 
enough temperature to form a ring of litharge 
crystals (“ feathers ”) around the cupel. This 
is liable to give too high results, as the lead 
may not be completely removed from the 
button. When cupelling with “feathers,” 
move button to hotter part of muffle to 
blick. 

8. Sometimes during cupellation the action 
stops, and the button solidifies. This is 
called “ freezing,” and is due to the oxides 
forming more rapidly than they can be ab¬ 
sorbed, or to the low temperature of the 


MOTES ON THE ASSAY OF ORES. 


37 


muffle. If tlie former, ail addition of lead 
will remedy it. If the latter, raise the tem¬ 
perature. The results are not reliable. 


15. Notes on Parting 1 . 

1. When the bead contains from two to 
three times as much silver as gold by weight, 
nitric acid will dissolve the silver. This 
separation is called “ parting.” Not all the 
silver will dissolve, but it is sufficiently accu¬ 
rate for ordinary work. 

2. If the bead is perfectly white, it usually 
needs no additional silver to “part” it. If it 
is yellow, it needs an addition of from 1^ to 
2^ times its weight of silver (according to 
the degree of yellowness), to part it. The 
button and the silver may be fused by the 
blowpipe on chaicoal, or by wrapping them 
in lead-foil and cupelling. Before parting 
the button, it is flattened by a hammer, and 
if large, passed through the rolls (Fig. 34), 


38 


1 MANUAL OF ASSAYING, 


after wliicli it is annealed by beating it to 
redness. 



Fig. 34 . 


Silver fuses at 954° C., and gold at 1045° C. 
The silver melts first and the gold sinks in it. 

































































NOTES ON TEE ASSAY OF ORES. 


39 


When the fusion is made by the blowpipe, 
care must be taken to continue the heat until 
the gold is fused. 

3. Parting can be effected in a test-tube, in 
a small porcelain crucible, or, if the button is 
large, in a parting-flask (Fig. 35). If the 
separation is made in a porcelain crucible, the 



Fig. 35 . 


gold is also dried and annealed in the same 
crucible. In annealing, the crucible should 
be heated to redness. The heat must be 
raised gradually to prevent the gold from 
being scattered by the steam formed. 

When the separation is made in a porcelain 
crucible, after pouring off the wash-water, 
bring the gold together, and turn the crucible 
so as to collect the remaining water on the 





40 


A MANUAL OF ASSAYING. 


opposite side from the gold. The water can 
then be removed by filter-paper. 

A needle, stuck into a soft piece of wood 
for a handle, is convenient to loosen the gold 
from the cup, after annealing. The gold can 
be weighed in this form, or some wrap it in 
lead-foil and cupel it. 

4. Use dilute acid, 1.16 sp.gr. (21° Baume), 
for the first boiling, and fresh acid of 1.26 sp. 
gr. (32° Baume) for the second boiling. If 
tlie acid is warmed before the bead is put 
into it, the gold does not break up into such 
fine particles. By boiling a second time, the 
silver is more completely removed, the gold 
becomes more compact, and there is less 
danger of loss. By boiling the acid after it 
is concentrated to about 1.42 sp. gr., it dis¬ 
solves gold in appreciable quantities. 

To prevent violent action and so keep the 
gold from breaking up into fine particles, 
after heating the dilute acid to nearly boiling, 
drop the bead into it and continue to heat it 


NOTES ON THE ASS A T OF ORES. 


41 


on a sand-bath or hot plate for ten or fifteen 
minutes; pour off the acid, add stronger acid, 
boil and proceed as directed above. 

5. If the gold, after parting, weighs more 
than one-third of the weight of the bead, the 
Sold contains silver and must be fused amiin 



Fig. 36 . 


with from 2 to 3 times its weight of silver, 
and again parted. 

6. If from to times as much silver as 
gold is present, the gold remains in one piece 
after parting; if much more silver is present, 
the gold breaks up into small particles, some 
of which may float on the surface of the acid. 






































42 


A MANUAL OF ASSAYING. 

By touching them with a glass rod, or by 
dropping water on them, they can be made to 
sink. Set the test-tube in the rack (Fig. 36) 
until all the gold lias settled, and bring the 
particles together by tapping the bottom of 



Fig. 36f/. 


the test-tube with the fingers, before pouring 
off the acid. 

7. If, in beginning to boil, the bead turns 
black and the action stops, it must be fused 
with additional silver. 

8. Small glass tubing in the acid while 

O O 

boiling will prevent “bumping.” 


















































NOTES ON THE ASSAY OF ORES . 


43 


16. Notes on the Scorification Assay. 

1. This method is especially applicable to 
rich gold and silver ores. The scorification 
assay gives higher (uncorrected) results for 
silver. 

2. If the slag is pasty, add borax. The 
slag may be rich. 

3. Borax makes the slag fluid, but if too 
much borax is used, the slag will cover the 
bath of metal too soon. 

4. If the muffle is not hot enough, when 
the scorifiers are charged in, gold may remain 
in the slag. 

O 

5. Pasty slag or slag from rich ores should 
be ground up, fluxed with a little borax and 
argol, and scorified as the ore. Use the same 
scorifier in which the first scorification was 
made, and cupel the button with the first one 
obtained. 

6. If the ore is low grade, make a number 
of assays, place the buttons together in a 


44 


A MANUAL OF ASSAYING. 


scorifier, add a little borax glass, and scorify 
them to the proper size for cupellation. In 
this case the slai»; need not cover the bath of 
metal. 

7. The treatment of other than silicious 
ores, and ores containing other elements, will 
be explained when they are taken up. 


17. Notes on the Fire Assay for Lead. 

1. The lire assay for lead gives only ap¬ 
proximate results. If the ore contains gold, 
silver, iron, copper, or other metals, some or 
all may be reduced with the lead. If the 
button is brittle, it contains antimony, sul¬ 
phur, etc.; if hard, copper, iron, etc. Arsenic 
carries lead into the slag, and forms with 
the iron a separate, hard, and brittle button. 
Some lead may volatilize, and some oxidize 
and £0 into the slas:. The button can be 
cupelled for the precious metals and the 
weight deducted. 


NOTES ON TEE ASSAY OF ORES. 


45 


2. If the assay is made in a crucible-fur¬ 
nace, the crucible should be covered. 

Avoid too high a temperature. Lead and 
lead sulphide are volatile at a high tempe ra¬ 
ture. The heat should not be above redness, 
at least for the first 20 minutes. 

3. Oxidized and carbonate ores need no 
nails. 

4. The assay can be poured, or allowed to 
cool in the crucible, after which the crucible 
is broken and the lead extracted. 

5. The slag can be assayed, and the lead 
recovered, added to the first button. 

6. Lead fluxes : 

Mix and take from 18 to 20 grams for 
5 grams of ore, and to ores containing 
sulphur, add 3 8-penny iron nails, or use a 
wrouglit-iron crucible. With ores contain¬ 
ing phosphorus, use additional borax glass 
to prevent pasty slag. 


46 


A MANUAL OF ASSA TING. 


1. Sodium bicarbonate. 
Potassium carbonate 

Wheat flour. 

Borax glass. 

Salt. 

2. (Plattner.) 

Potassium carbonate 
Sodium bicarbonate.. 

Flour. 

Borax glass . 

Sait.: . 



(1) or 

(2) 


16 

100 parts 


12 

50 “ 


12 

15 “ 


4 

25 “ 

. . cover 

cover 

(1) 

or (2) or (3) 

. 5 

6£ 

2 parts 

. G* 

5 

2 “ 

• H 

1 

1 “ 

. 2£ 

24 

1 “ 

cover cover 

cover 


3. Ore. 10 grams 

Potassium cyanide. 35 “ 

Salt. cover 

No nails. 


PbS + KCN = Pb + KSCN. 

Lead Sulphide Potassium Lead Potassium 

Cyanide Thiocyanate 

Potassium cyanide is a strong reducing 
agent, but, if used with ores containing iron, 
copper, and other metals, it reduces them 
also with the lead. 















CHAPTER TV. 


FLUXES AND REAGENTS. 

Sodium ..Bicarbonate , N"aHCO s , or its cor¬ 
responding potassium salt, KHCO s , acts as a 
basic flux, a desulphurizing agent, and in 
some cases, as an oxidizing agent. Heat 

/ O O 

reduces it to sodium carbonate, which on 
being fused with silica, forms fusible sili¬ 
cates, and liberates carbon dioxide. The 
carbon dioxide liberated oxidizes sulphur, 
and metallic iron, zinc, and other metals, 
which then go into the slag. With sulphide 
ores, under certain conditions, it forms so¬ 
dium sulphate and sodium sulphide. 

2NaHC0 3 + Heat = Na*C0 8 + C0 2 + H 2 0. 

166.80 * 

* The atomic weights from the sixth annual report of 
the committee on atomic weights are used in this book 
(see p. 136). 



48 


A MANUAL OF ASSAYING. 


A charge containing sodium bicarbonate 
should be heated gently at first, or the car¬ 
bon dioxide and steam, which are given off 
at a comparatively low temperature, may 
blow out some of the fine ore. The car¬ 
bonate fuses at about 800° C., and absorbs 
such infusible substances as lime, alumina, 
etc. 

When equal molecules of silica and so¬ 
dium carbonate are fused together, sodium 
bisilicate is formed, and carbon dioxide lib¬ 
erated. 

Na 2 C0 3 + Si0 2 - ]Sa,Si0 3 + CO,,. 

59.94 

W1 ien fusion takes place, the silica dis¬ 
places the CO,> in the sodium carbonate. 
The escape of the CO,, causes a brisk effer¬ 
vescence to take place. 

According to the above equations, it takes 
over 2.78 times as much sodium bicarbonate 
as silica to form sodium bisilicate. 

Sodium carbonate forms a double salt 


FLUXES AND REAGENTS . 


49 


with potassium carbonate, which fuses at a 
lower temperature than either alone. 

When silica, sodium carbonate, carbon, 
borax, and other substances are fused to¬ 
gether, as in an assay, of course many other 
reactions take place. 

Litharge , PbO, is used in the crucible 
assay of gold and silver ores. It is a basic 
flux, dissolves metallic oxides, oxidizes sul¬ 
phur and other oxidizable substances, and 
supplies the lead in the crucible assay. 

Nearly all litharge contains silver, the 
amount of which must be determined, when 
used in the assay for silver. It can be freed 
from red lead, Pb 3 0 4 , by fusing in a crucible, 
pouring, and keeping it from the air while 
cooling. It is claimed that red lead oxidizes 
silver and thus causes loss. 

With silica it forms a lead silicate. 

PbO + SiOo = PbSi0 3 . 

221.24 59.94 281.18 

It takes over 3.69 parts of lead oxide to 


50 


A MANUAL OF ASS A TING. 


one part of silica by weight to form lead 
silicate, which is easily fusible, and more 
fluid, when fused, than sodium silicate. It 
forms fusible double silicates, but has no 
action on lime or magnesia except in the 
presence of silicates and borates. 

Metallic oxides that are infusible or almost 
infusible alone are easily dissolved b} r lead 
oxide, with which they form a basic slag, 
which attacks the crucible by uniting with 
the silica in the crucible. 

Borax , NaoB 4 0 7 .—The unfused or crystal¬ 
lized borax, Na,B 4 0 7 , lOhLO, contains over 
47 per cent water. When mixed with the 
charge of ore and flux, the fused borax 
(borax glass) should be used, as the unfused 
borax is apt to cause loss by swelling and 
thus forcing part of the charge out of the 
crucible. It is an acid flux, and will flux 
sulphides, arsenides, metallic oxides, lime, 
etc. It also forms fusible compounds with 
silica. 


FLUXES AND REAGENTS. 


fl 

Silica, SiOo, is an acid flux. It forms 
compounds with all the bases, and is used in 
the assay of ores containing lime, magnesia, 
baryta, iron, etc. Pulverized silica (pure 
white quartz) should be used. 

As a substitute, ground glass can be used. 
Window-glass is probably the best, which is 
a silicate of sodium and calcium. Bohemian 
glass is a silicate of potassium and calcium, 
and is not easily fusible. Bottle-glass is a 
silicate of sodium, aluminum, calcium, iron, 
etc. Flint glass contains lead, and hence 
cannot be used in the assay for lead. Enam¬ 
elled glass should not be used, as it contains 
arsenic, antimony, tin, etc. 

Flour .—Wheat flour is a strong reducing 
agent. One part of flour will reduce about 
15 parts of lead from lead oxide. 

Argol is a reducing agent, and basic flux. 
It contains other carbonaceous matters than 
the pure potassium bitartrate, KHC 4 H 4 0 6 , and 
therefore has a greater reducing power. Heat 



52 


A MANUAL OF ASSAYING. 


changes it to potassium carbonate and carbon. 
Its reducing power can be determined by 
fusing it with litharge and sodium bicarbon¬ 
ate. One part of argol will reduce from 5 to 
8J parts of lead. 

Potassium Cyanide , KCN, is a strong re¬ 
ducing and desulphurizing agent. It com¬ 
bines with oxygen, forming cyanate, 

PbO + KCN = Pb + KCNO ; 
and with sulphur, forming thiocyanate, 

PbS + KCN - Pb + KSCN. 

Potassium cyanide is extremely poisonous. 

Charcoal. —Powdered wood-charcoal is 
used. It is a reducing agent. It absorbs 
water and gases, and has about 8 per cent 
ash, 2b per cent hydrogen, per cent oxy¬ 
gen, and 93 per cent carbon. At low tem¬ 
peratures it forms carbon dioxide ; and at high 
temperatures, carbon monoxide, when heated 
with metallic oxides, from which it takes the 
oxygen. As its reducing power varies under 



FLUXES AND REAGENTS. 


53 


different conditions, its reducing power 
should be determined under the conditions 
under which it is to be used. Ordinarily 1 
part of charcoal reduces from 20 to 30 parts 
of lead. 

Iron in the form of nails and wire is used 
in the assay of sulphide ores. It forms iron 
sulphide with the sulphur, which is dissolved 
by the slag, if only a moderate quantity is 
present. A large quantity will form a sepa¬ 
rate layer of matte. 

Potassium Nitrate , KN0 3 (nitre, or salt¬ 
petre), oxidizes most oxidizable substances. 
It melts at 339° (Person), 352° (Carnelly); 
and, at a higher temperature, it is decom¬ 
posed, yielding a large volume of oxygen. 
The oxygen combines with the sulphur of 
sulphide ores, and also oxidizes most of the 
metals except gold and some of the platinum 
group. One part of nitre oxidizes about 4 
parts of lead. 

Salt y sodium chloride, NaCl, is used as a 


A MANUAL OF ASSAYING. 


04 

cover. In an open crucible, it melts and vol¬ 
atilizes at a red heat, and forms a liquid cover, 
which excludes the air and prevents loss by 
ebullition. It washes the sides of the cru¬ 
cible, and forms fusible compounds with sili¬ 
ca, antimony, and arsenic. 

Metallic Lead , in the form of sheet lead, is 
used in cupelling beads and in the bullion 
assay. Granulated lead (test-lead) is used in 
the scorification assay. As nearly all lead 
contains silver, its silver contents should be 
determined, and the proper correction made, 
when used in the assay for silver. 

Lead acts as a basic flux, and a solvent or 
collector for gold and silver. 


CHAPTER V. 


SLAGS. 

One of the aims in making up an assay 
charge is to flux the ore so as to produce, 
when fused, a liquid slag. If the slag under 
this condition is not liquid, it may retain 
some of the precious metals. If the charge 
is of such a character that it fuses, and be¬ 
comes liquid at a low temperature, its reduc¬ 
ing power is diminished; and, if the slag 
becomes very liquid in the beginning of the 
fusion, the reduced lead particles may drop 
to the bottom of the crucible before they come 
in contact with all the gold in the charge. 

Slags are usually made silicates, which are 
made up of a basic oxide, as sodium oxide, 
lead oxide, lime, or baryta, combined with 
silica, which is acid in character. 


55 


56 


A MANUAL OF ASSAYING. 


Silicates are classified as subsilicates, mono- 
silicates, bisilicates, etc., according to the ratio 
of the oxygen in the base to the oxygen in 
the silica. 


Name. 

Sodium Silicate. 

Oxygen Ratio. 

Subsilicate. 

4Na 2 0.Si0 2 

2 : 1 

Monosilicate. 

2Na 2 0.Si0 2 

1 : 1 

Bisilicate. 

Na 2 0.Si0 2 

1 : 2 

Trisilicate. 

2Na 2 0.3Si0 2 

1 : 3 

Sesquisilicate. 

4Na 2 0.3Si0 2 

2 : 3 


The fusibility of a slag depends on the 
character of the bases, and on the percentage 
of silica it contains. The silicates of lime 
and alumina are the least fusible. Sla^s of 
the composition CaO.SiCb and 4Ca0.3Si0o are 
fusible, and those of a higher percentage of 
lime are almost or entirely infusible at the 
temperature of the assay-furnace. 

CaC0 3 + Heat = CaO + C0 2 . 

99.31 

CaO + Si0 2 = CaO.SiOo. 

59.94 














SLAGS. 


57 


It takes over 1.6568 times as much lime¬ 
stone, CaC0 3 , as silica, SiCX,, to produce a slag 
of the composition CaO.SiCb; or, to one assa)- 
ton, 29.1666 grams, of limestone, it takes 
17.6041 grams of silica. 

Neither lime nor silica can be fused at the 
temperature of the assay-furnace; but, if 
they are pulverized and intimately mixed in 
the proportions given above, they unite, at 
the temperature attained in the furnace, 
forming a fusible compound (calcium sili¬ 
cate) called a slag. To this must be added 
litharge to supply the lead in which to col¬ 
lect the gold and silver. Sufficient flour or 
arffol is added to reduce a lead button Weigh¬ 
ing about 20 grams. Soda, litharge, and 
silica are added in such proportions as to 
make a liquid slag (when hot), which dilutes 
the calcium silicate, thus making it more 
fluid, in order that the reduced metallic par¬ 
ticles of lead, gold, and silver can sink to the 
bottom of the crucible on account of their 
greater specific gravities. 


58 


A MANUAL OF ASSA YING. 


A charge for a gangue of limestone would 
be about as follows : 

Limestone. 1 A. T. 

Silica. liA. T. 

Sodium bicarbonate. ... 42 Grams. 

Litharge.42 “ 

Flour. 1.7 “ 

Borax-edass.10 “ 

O 

Salt.Cover. 

The borax fluxes the lime and other 
oxides, and helps to make the slag liquid. 
Borax becomes very liquid, when fused, so if 
not all the borax added is needed fur a flux, 
it will make the slag more liquid by simply 
diluting it. The exact proportions to make 
a certain slag with each ore cannot be calcu¬ 
lated, unless a chemical analysis is made of 
each ore. In assaying, this is out of the 
question, so the assayer is careful not to add 
an excess of a flux that is infusible in itself, 
but he adds an excess of a flux that is very 








SLAGS. 


59 


fusible, which, by merely diluting the slag, 
makes it more liquid. 

With magnesia, 4Mg0.3Si0.> and 2 MW). 
38i0 2 make fusible slags. 

O 


4MgC0 3 + Heat = 4MgO + 4 CO,. 


334.60 


4MgO + 3SiO, = 4Mg0.3Si0„. 

179 . 8-2 


It takes over 1.86 times as much magne¬ 
sium carbonate as silica to form the slag, 
4Mg0.3Si0 s ; or, to one assay ton, 29.166 
grams, of magnesium carbonate it takes 15.68 
grams of silica. 

With baryta, BaO.SSiCb and BaO.dSiO., 
make fusible slags. 

Silicates of alumina are not fusible alone at 
the temperature of the assay-furnace. If a 
base is added, as lime, lead oxide, iron oxide, 
etc., making them double silicates, they be¬ 
come fusible. A fusil >le slag can be made by 
adding sufficient lime and silica to make the 

O 


60 


A MANUAL OF ASSAYING. 


oxygen in the lime between one and two 
times that in tlie alumina, and the oxygen in 
the silica between one-half and twice the 
sum of the oxygen in the lime and the alu¬ 
mina. Clays are of various compositions, as 
2Al 2 0 3 .3Si0 2 , Al 2 0 3 .2Si0 2 .2H 2 0, etc. 

The most fusible silicates are those of lead, 
potassium, and sodium, after which come iron 
and copper. An excess of silica is an advan¬ 
tage in the fusibility of slags in which the 
base is lime or magnesia, but a disadvantage 
in those in which the base is sodium, lead, 
etc. The subsilicates, or basic silicates, are 
the most fusible ; and the fusibility of a slag 
decreases as the proportion of silica increases, 
except in lime and other silicates, already 
noted. Double silicates (silicates having two 
bases) are usually more fusible than those 
that have only one base. 


CHAPTER VI. 


THE ASSAY OF SO-CALLED REFRACTORY ORES. 

The assaying of silicious gold and silver 
ores has been discussed in the previous chap¬ 
ters. When an ore is oxidized, or contains 
sulphur, antimony, arsenic, tellurium, etc., it 
needs a different treatment. 

Such ores should be fluxed with a view to 
keep sulphur, arsenic, etc., out of the lead 
button; and, if one assay ton of ore is taken, 
to reduce a lead button of from 20 to 30 
grams. If the button weighs less than 20 
grams, there is danger of leaving some gold 
in the slag, especially in rich ores. Large 
buttons give low results for silver, as silver 
is lost by being absorbed by the cupel, and 
by volatilization in proportion to the amount 
of lead present. 


61 


62 


A MANUAL OF ASSAYING. 


The crucible assay is preferred for low 
grade ores, as a larger amount of ore can be 
taken. For rich ores, especially for rich sil¬ 
ver ores, the scorihcation assay has advan¬ 
tages. 

Oi ■es containing sulphur, antimony, arsenic, 
etc., have a reducing effect; those containing 
the higher oxides of iron, copper, manganese, 
etc., have an oxidizing effect. The former 
may reduce too large a button; the latter 
too small a button, or none at all. The 
reducing action can be corrected by an addi¬ 
tion of nitre, and the oxidizing action by an 
addition of Hour, argol, or charcoal. Some 
ores contain a mixture of oxidizing and re¬ 
ducing agents. 

o o 

By making a preliminary assay, the proper 
amount of oxidizing; or reducing agents to 

O o o 

be added may be calculated. After some 
experience, the student will know, from the 
appearance of the ore, about how much of 
the one or the other reagent to add. 

O 


ASSAY OF SO-CALLED REFRACTORY ORES. 63 


Preliminary Assay.— If tlie ore contains 
sulphur, antimony, arsenic, or other reducing 
elements, take 5 grams of ore, 50 grams of 
litharge, 18 grams sodium bicarbonate, 5 
grams silica, borax cover. Put the charge 
into a 10-gram clay crucible, and proceed as 
directed under 6. Detach the lead button 
and weigh it. Let us assume, for convenience 
of calculation : 

i assay ton. 30 grams 

1 part of nitre oxidizes. 4 parts of lead (3$ to 4) 

Lead button reduced by 5 

grams of ore. 7 grams 

1 assay toil would reduce... 42 grams of lead 
This is in excess of the weight 

desired, about. 20 grams 

20-t- 4 (1 part of nitre oxi¬ 
dizes about 4 of lead). 5 grams of nitre to be added to 

one assay ton of ore 

Sometimes by usin^ the amount of nitre 
calculated from a preliminary assay, very 
little or no lead is reduced. This may hap¬ 
pen when tin ore contains much iron oxide, 
and some sulphur. The litharge combines 
with the iron oxide, and some of the lead 







64 


A MA N UA L OF A SSA YIY G 


unites with the sulphur. An addition of 
nitre or a large addition of litharge will 
remedy this. 

Suppose the ore has an oxidizing power. 
Take 5 grains of ore, 30 grams litharge, 18 
grams sodium bicarbonate, 4 grams silica, 1 
gram hour (or 2 grams argol), borax cover. 
Proceed as directed above. One gram of 
flour should reduce from 12 to 16 grams of 
lead, if the ore is neutral. From the results 
obtained, the weight of the reducing agent 
that must be added to bring down a button 

O 

of the proper weight can be calculated. 

Let us assume, for convenience of calcula¬ 
tion : 

1 assay ton.. 30 grams 

1 gram flour reduces. 14 grams lead (12 to 16) 

5 grams ore with 1 gram flour gave 11 “ “ 

Hence, 5 grams ore oxidized 

(14 — 11) . 3 “ “ 

1 assay ton (6 x 5 grams) will oxidize 18 “ “ 

To neutralize the oxidizing ef¬ 
fect, it will take (18 h- 14) ... 1 285 grams flour 

To bring down a button (23.8 

grams), it will take. 1.7 grams flour 

Or 1 assay ton of the ore requires 3 


(2.985) 






ASS A Y OF SO-CALLED REFRACTORY ORES. 65 


The oxidizing and reducing powers of 
ores are different under different conditions. 
When the charge is acid, the sulphur oxidizes 
to SOo ; and, when much soda is present, the 
sulphur oxidizes to S0 3 , and sulphates are 
formed. Under the latter condition more 
lead would be reduced. 

A preliminary assay cannot be made for 
each ore in an office where much assaying is 
done. 

Desulphurization by Means of Iron Mails. 
—Ores containing only a small percentage 
of sulphur can be assayed by adding two, 
three, or more (according to the amount of 
sulphur in the ore) 20-penny iron nails, and 
sufficient silica to make a subsilicate with the 
bases present, to the charge as directed to be 
made under 5. If lime or magnesia are 
among the bases, add silica to make the slag 
given in Chapter V. The sulphur forms iron 
sulphide with the iron, a certain amount of 
which dissolves in the slag. If more is 


66 


A MANUAL OF ASSAYING. 


formed than the slag can take up, a separate 
layer of matte is formed. If a matte forms, 
separate the lead button, grind up the matte 
and slag, mix with 1 assay ton litharge, 
1 gram flour (or 2 grams argol), nails and 
silica as directed above, and use borax for a 
cover. Proceed as in a regular assay. In 
such an assay the slag would be very basic, 
without the addition of silica, and would at¬ 
tack the crucible by combining with the sil¬ 
ica in the crucible. 

Cupel this button with the first one ob¬ 
tained, or, if too large for cupellation, scorify 
the buttons to the proper size. 

Or remove the matte from the slag, pul¬ 
verize it, put it into a scorifier, and roast it 
“ dead 11 (see under Roasting), then add the 
first button obtained, silica, test-lead, and 
borax-glass, and scorify as directed under 9. 

If a button is obtained in any assay that 
is very large, it should be scorified to the 
proper size. There is less loss in scorification 


ASSAY OF SO-CALLED REFRACTORY ORES. 67 

than in cnpellation ; but, when the lead in a 
button is small in proportion to the silver, 
there is more loss of silver in scorification 
than in cnpellation. 

If the button is of the light size, but hard 
from the presence of iron, copper, or other 
base metals, or brittle from the presence of 
sulphur, arsenic, antimony, etc., scorify it 
with from 10 to 25 grams of testdead and a 
little borax-glass. 

Roasting .—Ores containing a large percen¬ 
tage of sulphur should be roasted. If the ore 
contains iron pyrites, put 1 assay ton of the 
ore into a clay roasting-dish, and perform the 
roasting in a muffle. Keep the temperature 
low at first or the ore will fuse and agglomer¬ 
ate. The rapid disengagement of volatile 
elements would also cause loss mechanically. 
Raise the temperature gradually, and stir the 
ore with a stout wire or iron rod, made by 
flattening one end, and bending it at a right 
angle, about an inch from tlie end. When, 


68 


A MANUAL OF ASSAYING. 


on stirring, no more burning is seen, gradu¬ 
ally raise the temperature to a dull red heat. 
Then take the roasting-dish with the ore out 
of the muffle, and allow the ore to cool, or 
pour it on an iron plate to cool. When cold, 
if 1 assay ton was taken, mix it with 42 
grams litharge, 42 grams sodium bicarbonate, 
from l to 1 I assay tons of silica, according to 
the percentage of iron present; from 2 to 4 
grams flour, according to the amount of ses- 
(piioxide of iron formed; and use about 15 
grams unfused powdered borax for a cover 
(or mix with from 8 to 10 grams borax-glass, 
and use salt for a cover). 

If all the sulphur has been burned out 
(“ dead ” roasted), and the iron is oxidized 
to sesquioxide, it needs the reducing agent 
prescribed. If not all the sulphur is burned 
out, the ore may still have a reducing power; 
and the addition of a reducing agent may 
bring down too large a button. 

O o 

When the percentage of sulphur is very 


ASSA Y OF SO-CALLED REFRACTORY ORES. 09 

liigli, add an equal weight of silica to the ore 
before roasting, which will help to prevent 
the ore from agglomerating. Take the 
amount of silica added into consideration in 
fluxing the ore. 

Ores can also be roasted over the furnace 
in a smooth, chalked, cast-iron pan, or in a 
crucible in the crucible-furnace. Proceed as 
directed above, and, if the roasting is done in 
a crucible, use the same crucible in which to 
make the fusion. 

If sulphide ores are not roasted, oxysul- 
phurets * may form, which are very fusible, 
but resist reduction at the temperature of the 
assay-furnace, and carry silver into the slag. 
In the fusion of ores containing arsenic and 
antimony, arseniates and antimoniates are 
formed, which carry silver into the slag. 
These ores should be roasted. Mix them 
with silica before roasting ; and, after roast- 

* Ricketts and Miller’s Notes on Assaying, pp. 94 and 95 ; 
Hiorns’s Practical Metallurgy and Assaying, page 258. 





70 


A MANUAL OF ASSAYING . 


ing, add some powdered charcoal to reduce 
arseniates and antimoniates, which may have 
been formed. Burn out all the charcoal. 

When su ipi iatcs are formed during roast¬ 
ing that cannot be broken up at a dull red 
heat, mix the cool, loasted ore with some 
ammonium carbonate, cover, and heat until 
fumes cease. This converts the sulphates 
into ammonium sulphates, which are vola¬ 
tilized. Treat copper sulphide ore in this 
way. 

Corrected Assays .—Slags from rich ores, or 
from ores containing much ferric oxide, Fe._,0 3 , 
or slags containing many metallic oxides, 

O O J 

should be assayed, and the button added to 
the first button. The slag from ores contain, 
ing zinc, arsenic, and antimony usually con¬ 
tain silver, if tlie ore contained silver. The 
cupels absorb silver and gold to some extent. 
Cupels in which large buttons of silver were 
cupelled should be assayed. Oxides of the 
base metals carry gold and silver into the 


ASS A Y OF SO-CALLED REFRACTORY ORES. 71 

cupel. Copper oxide in particular carries 
much gold and silver into the cupel. 

Assay Charges for Slags and Cupels .— 
Slag: If one assay ton of ore was taken, mix 
the pulverized slag with 1 assay ton litharge, 
1 gram flour, silica, if basic, and use borax 
for a cover. A small amount of soda may be 
added. Charges should vary according to 
the character of the slag. Scorification slags 
generally need only a little flour or argol, and 
a little borax. Cupels: The phosphates 
present in the bone-asli make the slag from 
cupels pasty. Fluorspar or borax will make 
the slag fluid. For assaying a cupel in which 
a button of 20 grams or more has been cu¬ 
pelled, proceed as follows : Remove the sat¬ 
urated part of the cupel, pulverize it, mix it 
with 50 grams litharge, 30 grams sodium 
bicarbonate, and 30 grams borax-glass. The 
slag and the cupel from the same assay can 
be fused together, fluxed as follows : 50 grams 
litharge, 50 grams sodium bicarbonate, 1 



7 2 


A MANUAL OF ASSAYING. 


gram flour or 2 grams argol, from 45 to 50 
grams borax-glass; and an amount of silica 
according to the character of the slag. 

General Crucible Charges .—From the fore¬ 
going discussion, the student will see that 
different ores require different fluxes. For 
silicious ores free from sulphur, etc., the fol¬ 
lowing charge will answer: 

Ore. 1 A. T. 

Litharge. 42 grams 

Sodium bicarbonate. 42 grams 

Flour. 1.7 grams 

Cover.15 grams unfused borax 

For ores containing only a small amount 
of sulphur add to the above charge one, 
two, or more 20-penny iron nails, and silica 
in proportion to the bases present, as ex¬ 
plained in Chapter V. 

Roast ore containing much sulphur, arsenic, 
etc., add silica, and, if roasted “ dead,” add 
also from j to 1 gram flour to the above 
formula, according to the amount of sesqui- 
oxide of iron present. 







ASSA Y OF SO-CALLED REFRACTORY ORES. 73 


Ores with a gangue of lime or baryta need 

more soda, borax, and silica. 

Mitchell's Formula: 

Ore. 


. 1 A. T. 

Sodium bicarbonate. 


2 u U 

Litharge. 


, 5 “ “ 

Borax-glass. 


2 u u 

Salt. 


Cover 

And argol or nitre to bring 

down a 

button of 

the required size. 



Aaron's General Formu 

la: 


Ore. 

. 1 A. 

T. 

Litharge. 

11 “ 

a 

Soda. 

. 3 “ 

a 

Borax. 

1 u 

♦ ^ 

u 

Flour . 

JL_ « 

u 

Iron, 1 to 3 nails. 

Salt. 

. cover 



Melt and leave in strong tire about 20 
minutes after fusion. 

Some assayers reduce all the lead in the 
litharge used, and slag the gangue with borax, 













74 


A MANUAL OF ASSAYING. 


soda, and silica. Aaron was the first to de¬ 
scribe this method. Beginners usually do 
not succeed very well with this method. 

4 1 

Special Methods .—For the assay of ores 
and materials containing copper for gold and 
silver, see Chapter IX. 

Telluride Ores may be treated in a beaker 
with aqua regia (three parts of hydrochloric 
acid to one part nitric acid, 3IIC1 + HNO s = 
NOC1 + 2H 3 0 + CL), which dissolves the 
gold and the tellurium. Add excess of hy¬ 
drochloric acid, and heat until all the chlorine 
and hydrochloric acid are driven off. Filter, 
wash, and precipitate the gold and tellurium 
with a current of sulphur dioxide gas, which 
can be made by burning sulphur, or by treat¬ 
ing copper with sulphuric acid, Cu -f- 2ILS0 4 
— CuS0 4 + 2 FLO + SOo. Treat the precipi¬ 
tate with nitric acid, which dissolves the 
tellurium. Filter, dry the gold residue, wrap 
it in lead-foil with 2 h times its weight of 
silver, cupel, part, and weigh as usual. When 


Y OF SO-CALLED REFRACTORY ORES. 75 

much silver is present, or other interfering- 
elements, not all the gold may dissolve. 
Precipitate the gold and the tellurium in the 
beaker containing the residue, then dissolve 
the tellurium with nitric acid, filter, and 
wash the residue. Dry the gold and residue, 
and proceed as with a regular assay. If 
silver is also to be determined, precipitate 
the silver in the filtrate and proceed as 
directed above for copper ore. It is con¬ 
venient to treat an assay ton of ore. 


CRUCIBLE CHARGES. (Tabulated from Ricketts and Miller’s Notes on Assaying). 


76 


A MANUAL OF ASSAYING. 


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TABLE OF CRUCIBLE CHARGES.* 


ASS A Y OF SO-CALLED REFRACTORY ORES. 7/ 




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Character of 
the Gangue. 

Neutral, no Pb_ 

No bases. 

No bases. 

Basic, no Pb. 

Basic, with BaSG 4 

Lead 84 per cent... 

Silicious Pb 42 per 
cent. 

Ore. 

Oxidized. 

Quartz. 

N 

■u 

U 

0 

3 

o 

Oxidized. 

Oxidized. 

Galena. 

Galena. 


* Furman’s Manual of Assaying. + Lead flux, p. 26, under 10. 





























































TABLE OF CRUCIBLE CHARGES-(Confm?tec/). 


78 


A MANUAL OF ASSAYING 


Remarks. 

Litharge added ac¬ 
cording: to the lead 
contents of the 

ore. 

Collect matte, if any, 

and scorify with 

lead button. 

Collect matte and 

scorify with lead 

button. If button 

is hard, add test- 

lead. 

Special method is 

preferable. 

If button is hard or 

brittle, scorify with 

lead. Scorification 

preferable. 

Special method. 

Scorify button. Sco¬ 

rification assay is 
preferable. 

If slag contains 

matte, add loop of 

iron wire. 

•JOAOQ 

borax 

borax 

borax 

borax 

borax 

salt 

salt 

L’olt 

3 1 

3 

. 

•ssnpi 

-xe.iog 'suif) 

: : : : : : 

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ao.ij jo sdooq 

! o o in m * * 

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: : : : : : 


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o mm o o o mo 

co co coco co i-i 

•xnn 

pBa r i jo -suif) 

o • mm o 

CO • y-i CO 

o 

•OJQ X ‘V 


Character of 
the Gangue. 

Neutral Fb JO per 
cent. 

None. 

Iron pyrites ... . . 

SiKcious. 

Silicious. 


Ore. 

Leadcarbonate 

Iron pyrites ... 

Copper pj-rites 

Lead matte.... 
Copper matte . 

Tellurides. 

Tellurides. 

Arsenical. 

Slags. 

























































ASSAY OF SO-CALLED REFRACTORY ORES. 70 


SCORIFICATION CHARGES. 


Ore. 

A. T. Ore. 

A. T. Test lead. 

Grams Borax- 

glass. 

Remarks. 

Quartz.'... 

Copper pyrites. 

7. 

H 

0.20 


7,0 

2* 

0.50 

Or 1.5 grams silica. 

Copper matte. 

7,0 

3 

1.50 

Gray copper. 

1 10 

2 

0 40 

Use litharge in place of lead 
in proportion totheamount 
of sulphur present. 

Iron pyrites. 

V 4 

3 

1.40 

Iron' oxide. 

7, 

U 

1.50 

3 grams silica; vary accord¬ 
ing to amount of silica in 
ore. 

Galena. 

7 a 

H 

3.00 

Use wire or nail in scorifier. 
Heat gently. 

Carbonate. 

1 5 

O 

4.00 


Chloride. 

76 

a 

1.00 

Low heat until covered, then 
raise heat. 

Blende. 

V* 

3 

1.00 

High temperature, and care 
in assaying. 

Arseidc and antimony. 

7s 

4 

1.50 

May need several rescorifica- 
tions. Powdered charcoal 
aids fusion. 

Telluride. 

7,o 

2 

0.50 

Sprinkle & A. T. litharge 
over the charge. May need 
several rescorificat ions 

with lead. 

Native An and Ag.. . . 

7,o 

a 

0.30 



Iii the treatment of ores containing sul¬ 
phur, arsenic, antimony, and tellurium, a 
preliminary roasting can he made; or they 
can be heated gently in the scoritier until 
roasted. Litharge can be used to advantage 
in all unroasted sulphuret ores. 



























80 


A MANUAL OF ASSAYING 


SCORIFICATION CHARGES.* 


Ore T V A. T. 

Grams 
of Test- 
lead. 

Grams 
of Borax- 
glass. 

Remarks. 

Galena... 

15-18 

up to 0.5 


Galena with blende and 




pyrite. . 

20-35 

0.4-0.8 


Iron pyrite. 

30-45 

0.3-0.8 


Arsenical pyrite........ 

45-50 

0.3-1.5 

High temperature. Ad¬ 
dition of litharge 
helps assay'. 

Gray copper. 

35-48 

0.3-0.5 

Low temperature. 

Blende. 

30-45 

0.3-0.6 

High temperature. Ad¬ 
dition of oxide of 
iron helps assay. 

Copper ores and mattes 

35-40 

0.3-0.5 

Low temperature. If 
necessary, the but¬ 
ton should be rescor¬ 
ified with lead. 

Lead mattes. . . 

25-35 

0..5-1.0 


Furnace accretions. 

25-50 

0.3-1.5 


Tellurides. 

Silicious . 

50 

25-30 

0.3 

Add a cover of lith¬ 
arge and rescorify 
the button. 

Basic. 

25-30 

0.5-2.0 

If the ore contains 
much lime or mag¬ 
nesia the addition of 
sodium carbonate 

helps the assay. 

Basic with barium sul- 



phate. 

25-30 

0.5-1.5 

Addition of sodium 
carbonate helps as¬ 
say. 

Lead carbonate. 

10-15 

up to 0.5 

Speisse. 

30-60 

0.3-0.5 

ligh temperature. Re¬ 
scorify the button 
with lead if neces' 
saiy. 


* Furman’s Manual of Assaying. 



































INFLUENCES OF BASE METALS ON CUPELLATION. 


ASSAY OF SO-CALLED IiEFit AC TORY 


ORES. 81 


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CHAPTER VII. 


AMALGAMATION AND CHLORINATION TESTS. 

Amalgamation and chlorination tests are 
usually intended to give an approximate in¬ 
dication of the percentage of gold and silver 
that can be extracted by these methods on a 
working scale. 

o 

Amalgamation Test. —Pulverize about 

5 lbs. of ore fine enough to pass through a 

40-mesh sieve. Sample it down to about 

1 lb. (see 3 ; and 1 under 12). Pulverize 

this sample fine enough to pass through 

an 80-mesh sieve, and assay it in the 

regular way. Mix the remaining ore and 

weigh out 3 lbs. and put J lb. of it into 

each of the twelve bottles on the shaking- 

frame (Fig. 37). Add sufficient water to 

82 


AMALGAMATION AND CHLORINATION. 83 

each bottle to make the ore of the consis¬ 
tency of very thin mud. Add about £ oz. 



Fig. 37. 


of clean mercury to the contents of each 
bottle, and run the frame at a high speed for 





















































































































































A MANUAL OF ASSAYING. 


O 4 

o± 

an liour or more. Then empty the bottles 
into a miner’s pan, and wash the tailings into 
another pan or tub. Pan out the mercury 
and the concentrates (particles of gold that 
will not amalgamate, sulphurets, etc.). Dry 
the concentrates, weigh, and assay them. 
Dry the tailings and assay them. Retort 
the mercury, or scpieeze it through a clean 
buckskin, put the amalgam left in the buck¬ 
skin into a porcelain crucible, and drive off 
the mercury by heating at first gently and 
finally to redness. Collect the gold, wrap it 
in lead-foil and cupel. Small amounts of 
amalgam can be treated with nitric acid, 
which dissolves the mercury and leaves the 
gold. 


Ore assayed. 3ozs. gold per ton 

Amount of ore taken for amalgamation.. 3 lbs 

Assay value for 3 lbs. of this ore. 2.16 grains gold * 

Gold extracted by amalgation from 3 lbs. 1.36 grains gold 

This corresponds to a yield of. 63 per cent of 

assay value 

Concentrates from 3 lbs. 3 ozs 


* See tables on page 136. 






AMALGAMATION AND CHLORINATION. 85 


One ton would give. 125 lbs 

Sixteen tons of ore would give. 1 ton of concen¬ 

trates 


Concentrates assayed per ton concentrates 16.48 ozs. 

The 125 lbs. in a ton of ore would give... 1.03 ozs. 

Tailings assayed.. 0.09 oz. 

The silver can be calculated in the same 
way. 

Retorting. — The mercury is usually 
squeezed through a buckskin and the amal¬ 
gam put into a retort (Fig. 38), which has 



Fig. 38. 


been rubbed with chalk on the inside. The 
amalgam should not be put into the retort in 
lumps, nor pressed down. Lute the lid on 
with a paste of flour, and fasten the clamp. 
Do not fill the retort more than about three- 










86 


A MANUAL OF ASSAYING. 


fourths full. Apply a low heat at the top and 
gradually increase the heat to redness. Afttr 
no more mercury comes over, increase the 
temperature to a cherry-red heat. During the 
heating, the condensing-pipe must be kept 
cool by keeping water running over it. The 
end of the pipe is usually placed in water. 
If the condensing-pipe sucks water at any 
time, it must be immediately lifted out of the 
water to prevent the water from being sucked 
into the retort and thus cause an explosion. 
It is safer to attach a canvas or rubber bag 
to the end of the pipe in the water. 

An amalgamation test can be made on a 
smaller scale by shaking, in a bottle, a pound 
of ore with an ounce of mercury. The prep¬ 
aration of the ore and the other operations 
are the same as already explained. 

Chlorination, Test .—Sample and assay 
the ore as directed under amalgamation 
assay. Weigh out one pound of the ore and 
roast it. After it is cold, moisten the ore 


AMALGAMATION AND CHLORINATION. 87 


sufficiently to make it cohere slightly when 
compressed in the hand. Put it into a wide* 
mouth bottle that has an opening at the bot. 
tom. The bottle should not be over half 
full. Pass a stream of chlorine into the 
bottle through the opening at the bottom. 
When chlorine begins to escape at the top, 
close the bottle and pass the chlorine a while 
longer. Then close the lower opening, and 
let it stand twenty-four hours. If at the end 
of that time, chlorine is still in excess, leach 
the ore with hot water until the filtrate gives 
no reaction for chlorine. Dry the residue and 
assay it. From the difference between this 
and the first assay, the approximate percent¬ 
age of extraction can be calculated. The 
gold in the solution can be precipitated with 
ferrous sulphate. Collect the precipitate and 
cupel. 


CHAPTER VIII. 

THE ASSAY OF ORE CONTAINING COARSE METAL. 

When ore contains scales of gold or other 
coarse metal that will not pass the sieve, it 
may be assayed by one of the following 
methods: 

1. Weigh (in grams) the pulp that passes 
the sieve, and determine its value by crucible 
or scorification assay in the regular way. 
Weigh (in grams) also the scales or other 
coarse metal, and determine its value in the 
same way. If the scales consist of gold and 
silver only, wrap them (or an equal part of 
them) in lead-foil, and cupel them in the 
regular way. If the gold only is to be deter¬ 
mined, add the necessary silver to insure sep¬ 
aration (see pp. 21 and 37) before cupelling 
the scales. 


88 


ASSAY OF ORE CONTAINING COARSE METAL. 89 

Example. —Suppose the pulp that passed 
the sieve weighed 112.664 grams, and the 
coarse metal weighed 4 grams. 1 assay ton 
of the pulp yielded 0.002 gram gold. 
112.664 -r- 29.166 (grams in one assay ton) 
= 3.86 assay tons in the pulp that passed 
the sieve. If 1 assay ton gave 0.002 gram 

gold, 3.86 assay tons would give 3.86 X 0.002 
gram = 0.00772 gram gold. The 4 grams 

coarse metal gave 0.014 gram gold. 0.00772 
+ 0.014 = 0.02172 gram gold in the whole 
sample. 

112.664 grams that passed the sieve + 4 
grams coarse metal = 116.664 grams, the 
weight of the whole sample. 

116.664 -7- 29.166 = 4 assay tons in the 
whole sample, which yielded 0.02172 gram 
gold. 1 assay ton (0.02172 a - 4) will give 
0.00543 gram, which = 5.43 ozs. Troy to 1 
ton ore of 2000 lbs. Avoirdupois (see assay 
ton weights, p. 9). The silver can be calcu¬ 
lated in the same way. 


90 


.4 MANUAL OF ASSAYING. 


2. If the coarse metal consists of copper 
or silver, dissolve it in nitric acid; if it con¬ 
sists of gold, dissolve it in aqua regia (311C1 
+ HNO s ). Evaporate the solution to a 
small bulk, and add it to the ore that passed 
the sieve in such a way that it will not run 
or soak through to the bottom. Dry the 
sample at a temperature not above 100° C. 
Then pulverize it again, pass it through the 
sieve, and mix it thoroughly. Assay it in 
the regular way. 

If copper is present, assay it by one of the 
methods given in Chapter IX. 

3. Place some of the pulverized ore on the 
bucking-board, or in a grinder, add the 
scales, and grind hard until the scales pass 
the sieve. Mix the ore thoroughly, and assay 
it in the regular way. 

By this method it is difficult to get assays 
that agree closely. 


CHAPTER IX. 


THE ASSAY OF COPPER ORES AND COPPER-BEAR¬ 
ING MATERIALS FOR GOLD AND SILVER. 

The operations in making these assays are 
not described in detail as the student, if lie 
has mastered the preceding chapters of this 
book, is familiar with the operations of the 
crucible and scorification assays. The cru¬ 
cible and scorification charges for the differ- 
ent gangue materials are also given on 
preceding pages. 

Ores and materials containing copper may 
be assayed by one of the following methods: 

1. T1 le gold can be determined by crucible 
assay, if the percentage of copper is not 
above about 15 per cent. 

Take J A. T. ore, or £ A. T., if the per¬ 
centage of copper is high. Add silica, and, if 


92 


A MANUAL OF ASSA TING. 


sulphur is present, roast the ore, cool, add 
ammonium carbonate, and heat (see roast¬ 
ing, and crucible charges for ores contain¬ 
ing copper). Scorify the button with silica, 
test-lead, and borax to remove copper, and 
cupel. 

If the ore is low grade, make a number of 
assays, and scorify the resulting buttons to 
remove copper, and to reduce them to the 
proper size for cupelling. 

Determine the silver by scorification assay. 
If the ore is low grade, make a number of 
assays, and scorify the buttons as directed 
above (see scorification charges for copper 
ore). 

2 . Ores and mattes containing much more 
than 15 per cent copper can be assayed by 
the scorification method (see scorification 
charges for ores and mattes containing cop¬ 
per). If the percentage of copper is high, 
take -^ 0 - A. T., and make from 3 to 10 scori- 
fications. Scorify the resulting buttons with 


THE .4 ASM Y OF COPPER ORES. 


93 


a little silica, test-lead (if they contain much 
copper, or if the amount of lead is small), 
and a little borax. 

3. The combination wet-and-drv method is, 
in general, as follows: 1 A.T. is treated 

with nitric acid until all the copper is dis¬ 
solved. The red fumes are expelled by boil¬ 
ing, after which the solution is filtered. If 
ore is treated, the residue is brought on to 
the filter, washed, and dried. Take the resi¬ 
due from the filter, burn the filter-paper in a 
porcelain crucible, and add the ash to the 
residue, flux and assay as usual. Add suffi¬ 
cient normal salt (NaCl) solution to the fil¬ 
trate to precipitate the silver. Avoid an 
excess, as silver chloride is soluble in salt 
solution. Allow the silver chloride to settle, 
then filter, wash the silver chloride on to the 
filter, put the filter-paper with the silver 
chloride into a scorifier, burn the filter in 
front of the muffle at a low temperature, add 
test-lead, scorify, and cupel. 


94 


A MANUAL OF ASSAYING. 


If copper borings are assayed, the residue, 
silver chloride, and both filter-papers can 
be put into the same scorifier (the papers 
burned) and scorified. 

There are various modifications of this 
method : 

( 1 ) Prof. Cabell Whitehead's Method* 
—Dissolve 1 to 4 A. T. in a large beaker 
(500 c.c. capacity), by the gradual addition 
of strong nitric acid ; drive off red fumes by 
heating in sand-bath ; add 50 c.c. saturated 
solution of lead acetate; stir; add 1 c.c. 
dilute sulphuric acid, and allow lead sulphate 
to settle. Filter ; wash with cold water, dry 
in scorifier; burn filter-paper; scorify with 
test-lead ; cupel, weigh, and part as usual. 

Dilute the filtrate to 1000 c.c. : divide in 
halves of exactly 500 c.c.; add to each satu¬ 
rated solution of sodium bromide so loim as 

O 

a precipitate forms. A large precipitate of 

* Transactions of the American Institute of Mining En¬ 
gineers, March, 1895. 






THE ASSAY OF COPPER ORES. 


95 


lead bromide collects and envelopes the 
silver bromide permitting immediate filtering 
without loss. Filter* wash with cold water* 
dry filters and precipitates ; brush into small 
crucibles; mix each with three times its 
weight of carbonate of soda and some Hour 
or argol as reducing agent; cover with borax- 
glass; fuse for lead buttons; cupel and 
weigh. The two results should agree closely. 

(2) Dr. (rodshalVs Method* —Dissolve 1 
A. T, of copper borings in dilute nitric acid 
(90 c.c. strong acid to 100 c.c. water). 
Evaporate the solution to expel free nitric 
acid, add 20 c.c. sulphuric acid, and continue 
the evaporation. Add hot water to take up 
the copper salts, dilute to about 800 c.c,, and 
allow to cool. Then pass a rapid stream of 
sulphuretted hydrogen into the solution for 
about two minutes. Stir the liquid contain¬ 
ing the precipitate, then allow the precipitate 

* Transactions of the American Institute of Mining En¬ 
gineers, February, 1900. 




96 


A MANUAL OF ASSAYING . 


to settle about half an hour, then filter 
rapidly. 

Dry the copper sulphide containing the 
gold and silver, burn the filter in a scorifier, 
and scorify the residue with 50 grams test- 
lead. 

When nitric acid acts on copper, nitrous 
acid is formed. Some gold is dissolved, in a 
hot solution, by the combined action of nitric 
acid and nitrous acid. By the combined 
wet-and-dry method, as given above, the 
average percentage of the loss of gold is 
high. For the determination of gold in cop¬ 
per-bearing materials, the scorification meth¬ 
od (see 2 above) gives much better results. 

(3) Mr. W. Randolph Van Liew has 
evolved a method * by which he claims an 
average gain of 6.75 per cent of gold in 
favor of his method, as compared with the 


* The Engineering and Mining Journal , April 21st and 
28th, 1900. 





THE ASSAY OF COPPER OPES. 


97 


usual wet-and-dry method. His method is 
substantially as follows: 

Take 1 A. T. copper, treat with 350 c.c. 
very cold water, and 100 c.c. nitric acid (sp. 
gr. 1.42), and set the beaker in a cool place 
(temperature should be kept down to 15° or 
16° C.). At the end of 18 or 20 hours, add 
sufficient nitric acid to dissolve the remain¬ 
ing copper (amount of acid will vary from 
0 c.c. to 30 c.c. nitric acid, sp. gr. 1.42). At 
the end of 24 to 26 hours, the solution of 
copper is complete. Remove the oxides of 
nitrogen by compressed air. Insert the 
pointed end of a pointed glass tube into the 
solution through which pass air into the 
solution, by means of a blower or other ap¬ 
paratus, until the red fumes are removed, 
which takes from 20 to 30 minutes. No 
heat is applied at any stage of the process. 

Add to the cold solution a slight excess 
(of from 2 c.c. to 4 c.c.) of normal NaCl 
solution. Experiments have shown that no 


98 


A MANUAL OF ASSAYING. 


difference was made whether the gold was 
filtered off before or after the addition of 
normal NaCI solution. 

Allow to stand over night, then filter, 
wash the entire contents to the point of the 
filter-paper, cover with from 4 to 6 grams 
test-lead, and, after the filter-paper lias 
drained, place it in a 24-inch scorifier, in the 
bottom of which there is about 1 gram test- 
lead. 

Dry and burn the paper in a muffle at a 
temperature below incipient redness. At 
the end of the yellow flame of the paper, 
remove the scorifier, and allow the charred 
paper to burn outside the furnace. By this 
slow combustion at a low temperature, loss 
of silver, by its reduction from silver chlo¬ 
ride, is avoided. 

At the end of about 20 minutes the paper 
will have burned. Now add from 8 to 4 
grams litharge, and from 3 to 4 grams borax- 
glass. 


THE ASS A Y OF COPPER ORES. 


99 


If all the copper has been washed out, and 
there are no impurities, no scorihcation is 
necessary. The operation is simply to melt 
and collect the gold and silver, after which 
the scorifier may be poured. Cupel the but¬ 
ton at a temperature giving heavy litharge 
feathers, and allow to blick at the same 
temperature. 

The time of operation is 48 hours. 

Mr. Van Liew reported 6 tests, by this 
method, which showed a loss of silver of 
from 1.2 to 2.2 per cent, or an average loss 
of silver of 1.7 per cent. Eighteen tests on 
c.p. gold showed a loss of gold of 0.00 per 
cent to 0.50 per cent, or an average loss of 
gold of 0.13 per cent. 


L.of C. 


CHAPTER X. 

THE DRY ASSAY OF MERCURY. 

The dry assay of mercury is effected in 
various ways: (1) The ore is pulverized and 
mixed with reducing agents, and then put in¬ 
to a retort, combustion-tube, or other distill¬ 
ing apparatus. The mercury is then driven 
off by heat, condensed, collected, and 
weighed. If the ore is rich and a large 
amount of it is taken, this method may give 
approximately accurate results. (2) Better 
results are obtained by receiving the mercury 
on gold-foil with which the mercury amalga- 
mates, but gold is expensive. After each 
assay, the mercury must be driven out of the 
gold-foil, which usually occasions a loss of 

gold. After a number of determinations, 

100 


THE DRY ASSAY OF MERCURY. 


101 


the gold must be remelted and rolled out 
ai^ain. 

O 

On account of these and other objections 
to the use of gold, Mr. Richard E. Chism 
employs silver as a recipient for the mercury. 
The following is condensed, with some 
changes, from his article * describing his 
method: 

Apparatus f and Flux. 

Heating Apparatus .—A glass alcohol-lamp 
can be used. 

lietort or Crucible .—Use a glazed white 
clay (or porcelain) crucible, in the form of a 
truncated cone, about 2 centimeters outside 
diameter at the bottom, and 3.5 centimeters 
diameter at the mouth; height about 4.5 cen- 

* Transactions of the American Institute of Mining En¬ 
gineers, October, 1898. 

Mr. Chism claims as original the use of silver for receiv¬ 
ing mercury (though this was suggested before), and the 
use of a separate vessel to cool the receiving surface by 
contact. 

f See Fig. 39. 




102 


A MANUAL OF ASSAYING. 


v g ~y 



L . ^ \ 


Fig. 39. —Apparatus for Mercury-assay one-half 

Actual Size. 

A, base of retort-stand. /?, spirit-lamp. (7, retort or an¬ 
nealing-cup. D D , retort stand ring, which serves as sup¬ 
port to the apparatus. E E , tin shields. F F, silver-foil 
for receiving the mercury. G , cooling-cup. 


















THE DRY ASSAY OF MERCURY. 


103 


timeters. The mouth of the crucible should 
have an even surface. 

Shield .—To prevent the direct heating of 
the upper part of the crucible and silver-foil, 
use a circular tin shield about 13 centimeters 
in diameter, with a hole in the center large 
enough to pass the crucible partly through, 
leaving about 1 centimeter of the crucible 
above the shield. 

The Recipient .—Use a piece of pure silver- 
foil (rolled silver) about 5 centimeters square, 
and about 0.02 millimeters in thickness, on 
which to receive the mercury. It should be 
large enough to cover the crucible and leave 

o o 

a margin all round of about one-half cen- 
timeter. 

Cooling-cup .—For cooling the silver-foil, 
use a silver dish of a wide pattern like an 
evaporating-dish. Silver is a good heat-con¬ 
ductor. A copper dish could be used. The 
bottom of the dish should be a little larger 
than the mouth of the crucible. Keep the 



104 


.1 MANUAL OF ASSAYING. 


bottom of the dish polished to enable you to 
discover any mercury that might soak through 
the silver-foil. Should this happen, drive off 
the mercury from the dish by heat, and repeat 
the assay with new silver-foil and less ore. 

Flux .—Use iron filings, the finer the better. 
They should pass a 60-mesh sieve. Remove 
most of the grease with strong alcohol, and 
then heat them to redness for some time in a 
muffle. Then keep the filings in a glass 
bottle with a rubber stopper. 

To Make the Assay. 

Take from one-half to one gram of the ore, 
prepared as directed under 3. If the ore is 
very rich, take less. Thoroughly mix the ore 
in the crucible with 5 grams of the prepared 
iron filings, and put about one gram of the 
iron filings on top of the charge as a cover. 
Now hang the crucible , by its tin shield, from 
the ring of a ring-stand. Carefully smooth 
the silver-foil (see The Recipient above), and 


THE DRY ASS A Y OF MERCURY. 


105 


ignite it in the flame of an alcohol-lamp. 
Care must be taken not to overheat the foil, 
or it will fuse. Cool the foil in a desiccator 
(Fig. 40), and then weigh it accurately on an 



analytical balance. Press it gently on the 
mouth of the crucible until it assumes the 
shape of the mouth of the crucible. 

Place the cooling-cup upon the silver-foil 
on top of the crucible, and till the cooling-cup 
with cold water (ice-water, if at hand). 

Place the alcohol-lamp under the crucible, 
and arrange it to give a flame about 4 cen¬ 
timeters high, which shall barely spread out 
at its point over the central part of the bot¬ 
tom of the crucible. 



















106 


A MANUAL OF ASS A YINO. 


Continue the heating from 10 to 15 min¬ 
utes. Ten minutes is too short for most ores, 
and anything over 15 minutes is apt to lead 
to loss of mercury. 

If ice-water is not used, it may be necessary 
to renew the water in the cooling-cup once or 
twice during the heating. 

O O 

When the heating is at an end, allow the 
crucible and contents to cool at least five min¬ 
utes. When the silver-foil is removed, a dis¬ 
tinct mercurial stain will be seen upon its 
lower surface, if there was the slightest trace 
of mercury in the ore. 

Convey the foil (under cover to avoid dust) 
to the balance, and weigh it. The increase in 
weight of the foil shows the amount of mer- 
cury on the foil. 

In order to check the first determination, 
and make sure that all the mercury has been 
collected, place the silver-foil on the crucible 
again, and heat the same charge about 10 
minutes more, allow to cool, and weigh again. 


THE DRY ASSAY OF MERCURY. 


107 


If the weight is constant, or if there is a slight 
decrease in weight, the amount of mercury 
obtained by the first weighing may be con¬ 
sidered correct. If more mercury has been 
collected on the second weighing, repeat the 
determination with a new charge, and heat a 
longer time—five or ten minutes longer than 
the first time. 

The foil can be preserved for future refer¬ 
ence, or the mercury can be driven off by 
carefully heating it in an alcohol flame; then 
the foil can be used for another determination. 

Polish the foil, if it is not bright, and care¬ 
fully anneal, cool, and weigh it just before 
making each assay, as directed above. 

Failures .—Failures may arise from too 
high or too long heating, from the foil being 
badly adjusted to the mouth of the crucible, 
or from the cooling apparatus not being prop¬ 
erly managed. 



CHAPTER XI. 


VOLUMETRIC DETERMINATION OF COPPER. 

Mr. Albert H. Low, assayer and analyti¬ 
cal chemist, of Denver, Colorado, has modified 
the cyanide method and the iodide method 
for the determination of copper. He has sent 
me the following descriptions of these meth¬ 
ods as modified by him : 

The Cyanide Assay for Copper. 

Standardization of the Solution. — The 
standard solution should contain about 21 
grams of pure potassium cyanide per 1000 c.c. 
Determine the exact standard as follows: 

Dissolve about 0.200 gram, accurately 
weighed, of pure copper-foil in 5 c.c. of 

strong nitric acid. Use a flask of about 250 

108 


VOLUMETRIC DETERMINATION OF COPPER. 109 


c.e. capacity. Without troubling to boil off 
the red fumes, add about 80 c.c. of water and 
10 c.c. of strong ammonia water. Cool the 
mixture to the ordinary temperature. Titrate 
with the cyanide solution, slowly and cau¬ 
tiously, so as to allow sufficient time for the 
fading of color due to each addition. When 

O 

the blue color has become perceptibly weaker, 
but is still fairly strong, dilute the solution so 
that the final bulk will be about 150 c.c. Now 
finish the titration by adding the cyanide in a 
slow and regular manner, finally one drop at 
a time until the blue tint is entirely discharged. 
The exact end-point is best observed by the 
aid of a vertical white background. From 
the amount of cyanide required, calculate the 
copper value per c.c. 

The accuracy of all subsequent work with 
the standard solution depends upon the oper¬ 
ators ability to duplicate the essential condi¬ 
tions of the final additions of cyanide. These 
are temperature, bulk of solution, and speed 


110 


A MANUAL OF ASSAYING. 


of working. Up to the point where the 
amount of cyanide added is insufficient to 
nearly discharge the color on long standing, 
the manner of adding it appears of no conse¬ 
quence; and the assay that has thus stood may 
be resumed and finished without detriment. 
The reaction proceeds rather slowly, and to¬ 
wards the end its speed is usually exceeded 
by that of the operator. It is therefore neces¬ 
sary, in finishing the titration, to proceed in a 
deliberate, methodical manner that can be 
duplicated in all subsequent work. 

Assay of Ores , etc .—Treat 0.5 gram in a 
flask of about 250 c.c. capacity with about 
6 c.c. of strong nitric acid. Boil gently nearly 
to dryness, and then add 5 c.c. of strong 
hydrochloric acid, and again heat until all 
soluble matter is taken up. Now add 5 c.c. 
of strong sulphuric acid, and boil until the 
white fumes are freely evolved. 

Time may be saved and bumping avoided 



VOLUMETRIC DETERMINATION OF COPPER. Ill 


by manipulating the flask in a holder over a 
naked flame. 

Allow to cool, add 20 c.c. of cold water, and 
heat to boiling. When an ore contains much 
iron, an insoluble anhydrous sulphate is apt 
to be present at this stage, which will only 
slowly dissolve in the warm dilute acid, 

%j / 

meanwhile remaining more or less in suspen¬ 
sion with a milky appearance. This anhy¬ 
drous sulphate retains copper. Do not proceed 
to filter, therefore, but keep the mixture warm, 
with occasional agitation, until the liquid 
clears and the residue appears normal. This 
may take several minutes. Finally filter, 
wash with cold water, and collect filtrate in a 
beaker about two and one-half inches in diam¬ 
eter. There should be about 75 c.c. of com¬ 
bined filtrate and washings. 

Place in the beaker a piece of stout sheet 
aluminum about five and one-half inches long 
and five-eighths of an inch wide, bent into a 
triangle so as to stand on edge. The same 


112 


xl MANUAL OF ASSAYING. 


triangle will last for many assays. Add one 
drop of a mixture of equal parts of strong 
hydrochloric acid and water, cover the beaker, 
and heat to boiling. 

A strong action is liable to occur unexpect¬ 
edly, and it is usually necessary to lower the 
heat when boiling begins. Boil gently for 
7 to 10 minutes, and then remove from the 
heat, and wash down the cover and sides of 
the beaker with cold water. Now add 15 c.c. 
of strong sulphuretted hydrogen water. This 
should produce little or no discoloration. 
Even though the copper be entirely precipi¬ 
tated, there is still danger of oxidation and 
loss during the subsequent washing unless 
sulphuretted hydrogen water be employed. 

Pour the solution through a 9 c.m. filter, 
and rinse on the copper with sulphuretted 
hydrogen water. Wash once or twice with 
the same water, and then finish with pure cold 
water. 

The metallic copper on the filter is more or 


VOLUMETRIC DETERMINATION OF COPPER . 113 


less mixed with copper sulphide, and there 
may be a little copper left adhering to the 
aluminum in the beaker. Pour over the latter 
5 c.c. of strong nitric acid, and then wash this 
into a second beaker, using not over 5 or 10 c.c. 
of water. Now transfer the filter and copper 
into the dilute acid, and warm gently until 
all is dissolved, and the separated sulphur ap¬ 
pears clean. 

If the ore contains silver, it should be pre¬ 
cipitated at this stage by the addition of a 
single drop of strong hydrochloric acid before 
the heating. Filter the copper solution into 
the original flask. Wash the filter thoroughly, 
but avoid getting the filtrate too bulky. Add 
10 c.c. of strong ammonia water to the filtrate, 
cool to the ordinary temperature, and titrate 
with the standard cyanide solution precisely 
as in the standardization. Dilute with water 
towards the end, if necessary, so as to obtain 
a final bulk of about 150 c.c. 

Should the presence of lead or other impur- 


114 


A MANUAL OF ASSAYING. 


it-y cause a milkiness in tlie blue solution, it is 
best to titter the mixture, when nearing the 
end of the titration, through a coarse rapid¬ 
running filter. From the number of c.c. of 
standard cyanide required, calculate the per¬ 
centage of copper in the ore. 

When the amount of silver is known, it 
need not be removed, but may be allowed for 
on the basis that 2As:=Cu. 100 ounces of sil- 

O 

ver per ton of 2000 lbs. will approximately 
equal 0.10 per cent of copper. Deduct, accord¬ 
ingly, 0.10 per cent of copper for every 100 
ounces of silver per ton. 

Copper Assay by the Iodide Method. 

Prepare a solution of sodium hyposul¬ 
phite containing about nineteen grams of 
the pure crystals to the liter. Standardize as 
follows: Weigli accurately about 0.200 gram 
of pure copper-foil and place in a flask of 
about 250 c.c. capacity. Dissolve in five c.c. 
of a mixture of equal volumes of strong 


VOLUMETRIC DETERMINATION OF COPPER. 115 

nitric acid (1.42 sp. gr.) and water; and then 
dilute to about fifty c.c., and boil until the 
red fumes are thoroughly expelled. This 
last is a very essential point. Remove from 
the heat and add a slight excess of ammonia 
water to the hot liquid. Ordinarily it suf¬ 
fices to add five c.c. of strong ammonia (0.90 
sp. gr.). Now add acetic acid in slight ex¬ 
cess,—say three c.c. of the 80 per cent acid 
in all. Cool to ordinary temperature and 
add three grams of potassium iodide, or five 
c.c. of a solution containing sixty grams of 
potassium iodide in 100 c.c. Cuprous iodide 
will be precipitated, and iodine liberated ac¬ 
cording to the reaction 2(Cu.2G,H 3 0 2 ) + 
4KI = CuX + 4 (K.CoH 3 Oo) + 21. 

The free iodine colors the mixture brown. 
Titrate at once with the hyposulphite solu¬ 
tion until the brown tinge has become weak, 
and then add sufficient starch liquor to pro¬ 
duce a marked blue coloration. Continue 
the titration cautiously until the blue tinge 



116 


.1 MANUAL OF ASSAYING. 


I 

lias entirely vanished. When almost at the 
end, allow a little time after the addition of 
each drop to avoid passing the point. One 
c.c. of the hyposulphite solution will be 
found to correspond to about 0.005 gram of 
copper. In the assaying of ores, when half 
a gram is taken, one c.c. of the standard 
hyposulphite would then equal about one 
per cent of copper. The reaction between 
the hyposulphite and iodine is 2(NaoS 2 0 3 ) + 
21 = 2NaI + Na.S 4 0 5 . Sodium iodide and 
tetrathionate are formed. 

The starch liquor may be made by boiling 
about half a gram of starch with a little 
water, and diluting with hot water to about 
250 c.c. It should be used cold, and must be 
prepared frequently, as it does not keep well. 

The hyposulphite solution made from the 
pure crystals and distilled water appears to 
be quite stable, showing little or no variation 
in a month, if kept under reasonable condi¬ 
tions. 


VOLUMETRIC DETERMINATION OF COPPER. 117 


Treatment of Ores. 

To lialf a gram of the ore in a flask of 250 
c.c. capacity, add about six c.c. of strong ni¬ 
tric acid, and boil gently nearly to dryness. 
Then add five c.c. of strong hydrochloric 
acid and a^ain heat. As soon as the in- 
crusted matter has dissolved, add five c.c. of 
strong sulphuric acid, and boil until the more 
volatile acids are expelled, and the fumes 
of sulphuric acid are coming off freely. 
This is best done by manipulating the flask 
in a holder over a naked flame. Allow to 
cool and add 20 c.c. of cold water, and heat 
the mixture to boiling. Allow to stand, hot, 
until any anhydrous sulphate of iron is dis¬ 
solved, and then filter to remove more espe¬ 
cially any lead sulphate. Receive the filtrate 
in a beaker about two and a half inches in 
diameter. Wash flask and filter with either 
hot or cold water and make the volume of 
the filtrate about seventy-five c.c. Place in 


118 


A MANUAL OF ASSAYING. 


the beaker a piece of sheet aluminum pre¬ 
pared as follows : Cut a strip of stout sheet 
aluminum five-eighths of an inch wide and 
about five and one-half inches long, and bend 
this into a ring so that it will stand upon 
its etffie in the beaker. The same aluminum 

O 

may be used repeatedly, as it is but little 
attacked each time. Add one drop of a mix¬ 
ture of equal parts of strong hydrochloric 
acid and water, cover the beaker and heat to 
boiling. Allow to boil seven minutes, which 
will be sufficient to precipitate all the copper 
in any case, provided the bulk of the solu¬ 
tion does not much exceed seventy-five c.c. 
The aluminum should now appear clean, the 
precipitated copper being detached or only 
loosely adhering. Remove from the heat 
and wash down the cover and sides of the 
beaker with cold water. There is danger of 
the finely divided copper being slightly oxi¬ 
dized and dissolved during the subsequent 
washing. To prevent this, add at once 


VOLUMETRIC DETERMINATION OF COPPER. 119 


fifteen e.c. of strong hydrogen-sulphide 
water. If the amount of the precipitated 
copper is large, it is best to wash it by 
decantation, as will be subsequently de¬ 
scribed; but, for quantities not exceeding 
say 20 per cent, it is more convenient to pro¬ 
ceed as follows: Pour the clear liquid 
through a nine cm. filter and then wash on 
the copper with cold \ s. water. The beaker 
and aluminum, which may still retain some 
adhering particles of copper, are now set 
aside temporarily. Wash the copper on the 
filter several times with cold water, and then 
place the original flask under the funnel. 
Now pour over the aluminum in the beaker 
five c.c. of a mixture of equal volumes of 
strong nitric acid (1.42 sp. gr.) and water, 
and heat to boiling. Do not prolong the 
boiling, or the aluminum will be unneces- 
sarily attacked. Pour the hot acid very 
slowly over the copper on the filter so as 
to dissolve it all, and then wadi beaker and 


120 


A MANUAL OF ASSAYING. 


filte r several times. Heat the solution in 
the flask to boiling and thoroughly boil off 
the red fumes; then replace the flask under 
the funnel and pour five c.c. of strong bro¬ 
mine water through the filter. The bro¬ 
mine cleanses the separated sulphur left on 
the filter, and also insures the highest oxi¬ 
dation of any arsenic or antimony present 
in the filtrate. If five c.c. are insufficient to 
impart a permanent tinge to the filtrate, 
more must be added. Again wash the filter 
and then boil the filtrate, which usually does 
not exceed seventy-five c.c. in bulk, to 
thoroughly expel the excess of bromine. 
Itemove from the heat and add ammonia 
water in slight excess (ordinarily add five 
c.c. of strong ammonia), and then acidify 
with acetic acid. The addition of three c.c. 
of the glacial acid is usually sufficient. A 
large excess of acetic acid does no harm, but 
is not necessary, except in the presence of 
sufficient arsenic to cause a precipitate of 


VOLUMETRIC DETERMINATION OF CO PEER. 121 


copper arseniate. This may require consid¬ 
erable acetic acid for its solution. If not dis¬ 
solved at this stage, it is taken up slowly 
later on, and the titration may become very 
tedious before the true end-point is finally 
reached. Proceed with this acetic acid solu¬ 
tion precisely as described in the standardiza¬ 
tion of the hyposulphite, and calculate the 
percentage of copper from the amount of 
hyposulphite required. 

With high percentages it is advisable to 
wash the precipitated copper by decantation 
as follows: Transfer the liquid and copper 
in the beaker to the original flask, and set 
the beaker and aluminum aside temporarily. 
Decant through the filter and wash the cop¬ 
per perhaps three times by decantation with 
cold dilute \ s. water, using about 20 c.c. 
each time. Now place the flask under the 
funnel, heat the five c.c. of acid in the beaker 
as before, and pour it through the filter. Do 
not wash for the moment, but remove the 


122 


A MANUAL OF ASSAYING. 


flask, replacing it under the funnel with the 
beaker, and heat the acid until all the copper 
is dissolved. Now return the flask under 
the funnel and proceed with the washing. 
Boil off the red fumes and continue as 
described above. 

Notes .—According to the equation pre¬ 
viously given, half a gram of pure copper 
requires 2.62 grams of potassium iodide. 
While direct experiment shows this to be 
apparently true, yet with only the theoreti¬ 
cal amount of iodide present the reaction is 
slow, and in fact does not appear to proceed 
to completion until during the titration, 
which is thereby unduly prolonged. It is 
best, therefore, to use not less than three 
grams in any case. An excess does no harm. 
Zinc and silver do not interfere. Lead and 
bismuth are without effect, except that by 
forming colored iodides they may mask the 
approach of the end-point before adding 
starch. Lead is practically removed as sul- 


VOLUMETRIC DETERMINATION OF COPPER. 123 


pliate by the first filtration. If bismuth is 
suspected in appreciable amount, simply add 
the starch earlier in the titration. Arsenic 
and antimony when fully oxidized as de¬ 
scribed have no influence. The return of the 
blue tinge in the titrated liquid after long 
standing is of no significance, but a quick 
return, which an additional drop or two of 
the hyposulphite does not permanently des¬ 
troy, is usually an evidence of faulty work. 


CHAPTER XII. 


VOLUMETRIC DETERMINATION OF LEAD. 

Some assayers check their fire-assays of 
lead by a wet method. For the convenience 
of those who desire a rapid method to check 
their fire-assays, the ammonium molybdate* 
method is here given. 

This method is based upon the fact that 
ammonium molybdate, when added to a hot 
solution of lead acetate, will give a precipitate 
of molybdate of lead (PbMo0 4 ), which is in¬ 
soluble in acetic acid. Any excess of ammo- 
nium molybdate will give a yellow color with 
freshly prepared solution of tannin. 

Indicator .—A freshly prepared solution of 
1 part tannin in 300 parts water. 

Standard Solution .—The standard solution 

* H. H. Alexander, The Engineering and Mining Journal, 
April 1st, 1893. 


124 






VOLUMETRIC DETERMINATION OF LEAD. 125 

of ammonium molybdate is prepared by dis¬ 
solving 9 grams of ammonium molybdate in 
1000 e.c. of water. One c.c. of this solution 
will equal about 0.01 gram lead. If the solu¬ 
tion is not clear, it can be made so by adding 
a few drops of ammonium hydrate. 

Standardizing .—Weigh out 0.300 gram of 
pure sulphate of lead, and dissolve it in hot 
ammonium acetate; then acidify with acetic 
acid, and dilute with hot water to 250 c.c. 
Heat to boiling, and add from a burette the 
molybdate solution, prepared as above men¬ 
tioned, until all the lead is precipitated as a 
white precipitate. This is ascertained by 
placing drops of tannin solution upon a por¬ 
celain plate, and then to these drops is added 
a drop of the solution tested, after each addi¬ 
tion of ammonium molybdate. As long as 
the lead is in excess, no coloration is pro¬ 
duced ; but as soon as the molybdate is in ex- 
cess, a yellow color is produced with the tan¬ 
nin (0.300 gram PbS0 4 X 0.68317 = 0.20495 



126 


A MANUAL OF ASSAYING. 


gram Pb). The solution in the beaker should 
be stirred after each addition of molybdate 
solution before the drop-test is made. From 
the number of molybdate solution used, the 
value of one c.c. is calculated in the usual way. 

Assay .—To determine the lead in ore or 
other material, weigh out 0.5 or 1.0 gram of 
the substance, according to the percentage of 
lead. If the substance contains 30$ or more 
lead, 0.5 gram will be sufficient. Treat the 
sample weighed out in a porcelain casserole 
with 15 c.c. strong nitric acid and 10 c.c. 
strong sulphuric acid. Heat until all the 
nitric acid is expelled, which is indicated by 
fumes of sulphuric anhydride coming oil*; 
then allow it to cool, and dilute with cold 
water; stir, then boil until all soluble sul¬ 
phates are brought into solution. Now filter, 
leaving as much of the precipitate in the 
casserole as possible. Now wash twice with 
hot dilute sulphuric acid and once with cold 
water. The sulphate of lead remaining in the 



VOLUMETRIC DETERMINATION OF LEAD. 127 


casserole is next dissolved with Lot ammo¬ 
nium acetate; pour the Lot solution on tLe 
filter and allow it to run into a clean beaker. 
TLis operation is repeated until all tLe sul- 
pLate of lead is dissolved. Wasli out tlie 
casserole thoroughly witL Lot water into the 
filter. Acidify tlie solution with acetic acid, 
dilute up to 250 c.c. with Lot water. Now 
lieat to boiling and run in from a graduated 
burette tLe standardized solution of ammo¬ 
nium molybdate until all tLe lead is precipi¬ 
tated, stirring tLe solution after eacli addition 
of molybdate, and testing a drop of tlie solu¬ 
tion, after each addition of molybdate, on a 
porcelain plate with tlie tannin solution. 
From tlie number of c.c. of tlie molybdate 
solution used, calculate tlie per cent of lead. 

TLe lead determination can easily be made 


in 30 minutes. 

Arsenic, antimony and phosphorus do not 
interfere with this method, as they pass 
through, the filter in solution. 


APPENDIX A. 

SUPPLEMENTARY NOTES ON THE ASSAY OF 

ORES. 

Cupels. —If the bone-ash used in making 

cupels is coarse, the cupels will be too 

porous, and much silver and some gold will 

be carried into the cupel. If the bone-ash is 

very fine and the cupels are compressed very 

hard, they will be too dense, may not absorb 

the litharge as fast as formed, and will crack 

in drying, and on becoming saturated with 

litharge. If the cupels are not compressed 

hard enough, they will be too porous; if 

compressed too hard, they will be too dense. 

The results in these cases are the same as 

stated above (see also p. 3). Some assayers 

take one part of wheat hour and mix it thor- 

128 


APPENDIX A. 


129 


oughly with ten parts of bone-ash before 
moistening, and compress the cupels hard. 
On heating the cupels in the muffle before 
the buttons are dropped into them, the flour 
burns out, leaving the cupels porous. 

From what has been stated, it is evident 
that cupels should be made of fine bone-ash, 
and of such hardness that they will absorb 
the litharge, and as little of the precious 
metals as possible. A cupel made of fine 
bone-asli, and of such hardness that, when 
dry, a fall of two to two and one-half feet 
will not break it, will absorb very little 
silver. By filling the cupel-mould about 
two-thirds full of coarse bone-ash, and the re¬ 
mainder, which forms the bowl of the cupel, 
with extra fine bone-ash, a cupel can be made 
that will absorb the litharge, and will absorb 
very little silver. 

Cupels will be stronger and less liable to 
crack in drying, if a strong solution of sodium 
or potassium carbonate is used instead of 


130 


A MANUAL OF ASSAYING. 


water to moisten the bone-ash. The bone- 
ash should not be sufficiently moistened to 
feel wet (see p. 1). 

Cupels should be dried slowly before they 
are used. If they are put into the hot muffle 
while moist, they will fall to pieces. If but¬ 
tons are dropped into the cupels before all 
the moisture and the gases are expelled, loss 
may result from spirting. 

Sampling .—Great care should be taken in 
taking an average sample of ore. Unless the 
sampling is properly done, the results of the 
assay are worthle. s. Not only should great 
care be taken in taking an average sample 
across the vein of ore in the mine at different 
places, but also in sampling the ore so taken 
for an assay sample (see !*• 29). 

Fluxing and Fusion .—In the chapter on 
slags, it has been explained that assay charges 
are made up of basic and acid substances in 
such proportions that they will combine and 
form liquid slags. The general reactions are 



ArPENDIX A. 


131 


indicated, but, as stated on page 49, when so 
many substances are thrown together, many 
other reactions take place. 

The gangue must be so fluxed that all be- 

o o 


comes fusible, or the precious metals cannot 
be released, and collected in a button of lead 
in the bottom of the crucible. For example, 
if ferric oxide, Fe 2 0 3 , forms part of the gangue 
materials, the charge must contain sufficient 
reducing agents to reduce the ferric oxide 
to ferrous oxide, FeO. The ferric oxide 
would not fuse, but would be entangled or 
absorbed by the soda or slag, and the gold 
and silver contained in the ferric oxide would' 
be carried into the slag with it; but, if the 
ferric oxide is reduced to ferrous oxide, the 
ferrous oxide unites with the silica, etc., and 
the compound so formed becomes fusible, 
and allows the precious metals to drop to the 
bottom of the crucible by virtue of their 
greater specific gravities (see also under Cor¬ 
rected Assays). 


132 


A MANUAL OF ASSAYING. 


Cupellation .—In the operation called cu- 
pellation, the lead is oxidized forming lith¬ 
arge. The other base metals also oxidize. 

O 

Lith arge is fusible at a bright red heat, and, 
when fused, has the property of dissolving 
or absorbing oxides of other metals. Bone- 

O 

asli lias the property of absorbing 'melted 
litliarge, and a certain amount of other oxides 
that may be dissolved by the litharge. Gold, 
silver, platinum, and some of the rarer metals, 
do not oxidize by this operation, and, there¬ 
fore, are not dissolved or absorbed by the 
litharge, and hence not carried by it into the 
bone-ash. 

When a large amount of base metals is 
present, the litharge formed may not be suf¬ 
ficient to carry all the oxides into the cupel. 
If this is the case, some of the oxides remain 
on the cupel, known as a scoria. An addi¬ 
tion of lead might have carried all the oxides 
into the cupel. A scoria also forms on the 
cupel if the lead button is not entirely freed 


APPENDIX A. 


133 


from slag. The scoria may have entangled 
some lead which carried the gold and silver. 
Hence the scoria may contain some of the 
P 1 •ecious metals, which can be recovered by 
crucible or scorification assay. 

After charging in the buttons, the muffle 
should be closed until they uncover. The 
muffle should be hot enough to start a rapid 
oxidation. Then the temperature should be 
lowered to form litharge crystals, and the 
ba tons should be allowed to blick at a higher 
temperature. 

The muffle can be cooled by checking the 
fire, or by putting cold scorifiers, crucibles, 
or cupels into the part of the muffle that is 
too hot, replacing them when hot, until the 
desired temperature is secured. 

As loss will result, if the button is 
moved on the cupel, it is safer to regulate 
the temperature as here directed, than to 
move the cupels as directed on pp. 19, 35, 
and 36. 


134 


A MANUAL OF ASSAYING. 


The assayer should aim to approach these 
somewhat ideal conditions: 

1. To flux the gangue so that every particle 
of it becomes fusible and forms a liquid slag. 

2. To reduce the least amount of lead that 
will just collect all the gold and silver. 

3. To have a cupel that is fine and hard 
enough to absorb all the litharge and none 
of the gold and silver. 

4. To oxidize the button in the least time 
possible, avoiding bad effects of too rapid 
oxidation. 

5. To have the muffle hot enough to start 
a rapid oxidation, then cool sufficient to form 
litharge crystals, and allow the buttons to 
blick at a higher temperature. 

Fire Assay of Lead Ore. —When the 
muffle is at a low red heat, put the crucibles 
with the charges into the muffle, and keep 
the temperature low enough to prevent spirt¬ 
ing. Do not allow the temperature to get 
above redness, and allow the crucibles to re- 



APPENDIX A. 


135 


main in tlie muffle from an hour to two 
hours. The time will depend somewhat on 
the proper regulation of the temperature. 
If the blue flame above the crucibles 
u jumps,” the muffle is too hot, and unless 
the temperature is immediately lowered, the 
assay will be defective. After the blue flame 
ceases, allow the assays to remain in the 
muffle a short time longer. Just before pour¬ 
ing, the temperature should be raised. 

If the muffle is left partly open to watch 
the working of the assays, the opening in the 
back part of the muffle should be closed with 
fire-clay, to prevent a draught, of air through 
the muffle. 

By this method higher results can be 
obtained than by the method described on 


APPENDIX B, 


TABLES. 

Atomic Weights. 


H. = 1 

Aluminum. 26.91 

Antimony... 119.52 

Barium. . . 136.39 

Boron. 10.86 

Calcium. 39.76 

Carbon . 11.91 

Chlorine. 35.18 

Chromium,.. 51.74 

Cobalt. 58.55 

Copper. 63.12 

Fluorine. 18.91 

Gold. 195.74 

Hydrogen. 1.000 

Iron. 55.60 

Lead. 205.36 

Lithium. 6.97 


Magnesium .... 

H. = 1 
. 24.10 

Manganese. 

_ 54.57 

Mercury. 

.... 198.49 

Nickel. 

. 58.24 

Nitrogen. 

. 1393 

Oxygen.. 

.... 15.88 

Platinum. 

... 193.41 

Potassium.. .. 

. 38.82 

Selenium. 

. 78.58 

Silicon. 

. 28.18 

Silver. 

... 107.11 

Sodium. 

. 22.88 

Sulphur. 

. .. 31.83 

Tellurium. 

. 126.52 

Tin. 

_ 118.15 

Zinc. 

. 64.91 


Troy Weight. 

24 grains = 1 dwt. 

480 “ = 20 “ = 1 oz. 

5760 “ = 240 “ = 12 “ = 1 lb. = 22.816 eu. in. of 

distilled water at 62° Falir. 

13G 































A MANUAL OF ASSAYING. 


137 


Avoirdupois Weight. 

1 drachm = 27.34375 grains Troy. 


16 

1 1 

= 1 oz.= 437.5 

u a 

256 

11 

= 16“= 1 lb. = 

1.2153 lb. Troy 

6400 

(< 

= 400 “ = 25 “ = 

1 quarter. 

25600 

u 

= 1600 “ = 100 “ = 

4 “ 

512000 

i i 

= 32000 “ = 2000 “ = 

o 

00 


= 20 cwt. = 1 ton. 


Metric, or French Weights. 


Grams. Troy Grs. 

1 Milligram = .001— .01543 

1 Centigram — .01 = .15432 

1 Decigram = ,1 = 1.5432 Troy Ozs. Troy Lbs. 

1 Gram = 1. = 15.432 = .032 = .00267 

1 Decagram = 10. =.321 = .02679 

1 Hectogram= 100. =. 3.215 = .26792 

1 Kilogram = 1000. =. 32.150 = 2.6792 

1 Myriagram= 10000. =. 26.792 

1 Quintal = 100000. =. 267.92 

1 Tonneau = 1000000. =.2679.2 

Avoir Ozs. Avoir Lbs. 

1 Gram = .03528 = .0022047 

1 Decagram = .3528 = .022056 

1 Hectogram= 3.52758 = .22046 

1 Kilogram = 35.2758 = 2.2046 

1 Myriagram =. 22.046 

1 Quintal =. 220.46 

1 Tonneau =. . 2204.6 

.064798 gram = 1 Troy grain. 

1 gram = 15.43235 Troy grains. 


1 A. T. = 29.166 grams = 450.0999 Troy grains. 

























' -l 






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FIRE BRICK 



SHELF AT E-F 

I 3 /ig IN. IRON i 

v_ y 



HORIZONTAL SECTIONS 

Scale, In. = 1 Ft. 


COAL-BURNIS 


























































































































































































































































































D 


B 



[To face page 131. Jj 














































































































































































































































































































































INDEX. 


A 

PAGB 

Amalgamation Test. 82 

Ammonium Carbonate, in roasting. . 70 

Ammonium Molybdate Method for Lead . 124 

Assay of Gold and Silver Ores. 10, 24, 61 

Corrected Assay. 70 

Notes on Assay of Ores. 29, 128-135 

Assay of Copper Ores for Gold and Silver... 91-99 

Ores containing Coarse Metals. 88 

Copper Materials for Gold and Silver.91-99 

Copper. 108 

Cupels. 71 

Lead. 26, 44, 124 

Mercury. 100 

Slags. 71 

Preliminary Assay. 63 

To make the Assay. 10 

To prepare the Assay. 5 

Assay-ton Weights. 9 

B 

Bicarbonate of Soda. 47 

Borax. 50 

139 


























340 


INDEX. 


C 

PAGE 

Charcoal. 52 

Chlorination Test. 86 

Copper, Determination of. 108 

Cyanide Assay. 108 

Iodide Assay. 114 

Ores, Assay for Gold and Silver. 91-99 

Materials, Assay for Gold and Silver.... .... 91-99 

Crucible Charges. 10, 58, 72, 76, 77, 78 

Cupels.1, 128 

Assay of. 71 

Cupellation. 17, 34 

Influence of Base Metals on. 81 

Notes on.34, 132 

I) 

Desulphurization by means of Iron Nails. 65 

Determination of Copper. 108 

Gold and Silver. 10, 24, 61 

in Copper Ore. 91-99 

in Copper Matte. 91-99 

in Copper. 91-99 

in Cupels.'. 71 

in Slags . 71 

F 

Fire-assay for Gold and Silver Ores (Crucible) 10, 24, 29, 61 

(Scorification). 24, 43 

Flour.,. 51 

Fluxes. 3, 46, 47, 76-80 

Fusion in Crucible. 13 

Notes on.!.32, 130 




























INDEX. 


141 


PAGE 

G 

Godshall’s Method. 95 

I 

Iron, Flux. 53, 104 

in Assays. 65 

L 

Lead, Determination by Fire-assay. 26, 44 

by the Wet Method. 124 

Notes on the Fire assay.44, 134 

Fluxes. 26, 46 

Litharge . 49 

M 

Mercury, Assay of. 100 

P 

Parting. 21 

Notes on. 37 

Potassium Cyanide. 52 

Potassium Nitrate. 53 

R 

Retorting. 85 

Roasting. 67 

with Ammonium Carbonate. 70 

S 

Salt. 53 

Samples and Sampling.29, 130 




















142 


INDEX. 


PAGE 

Scorification Assay. 24 

Notes on. 43 

Scorification Charges. . 79, 80 

Silica . 51 

Slags. 55 

Assay of. 71 

Sodium Bicarbonate. 47 

Special Methods. ...... 74 

T 

Tables...,. 130 

Atomic Weights . 130 

Avoirdupois Weight. 137 

Metric, or French Weights. 137 

Troy Weight. 130 

Tellurium Ores. 74 

Test-lead. 54 

V 

Van Liew’s Method. 90 

W 

Whitehead's Method. 94 




















Notes on Assaying. 

BY 

PIERRE de PEYSTER RICKETTS, E.M., Ph.D., 

Formerly Professor of Analytical Chemistry and Assaying, 

School of Mines, Columbia University, 

AND 

EDMUND H. MILLER, A.M., Ph.D., 

Instructor in Analytical Chemistry and Assaying, 

School of Mines, Columbia University. 

THIRD EDITION, REVISED. 

8vo. 320 pages. Thirty=nine Cuts. 

Cloth, $3.00. 

CONTENTS •— Part I. Introduction. Apparatus. Re¬ 
agents and Chemicals. Operations.— Part II. Dry or 
Fire Assays.— Part III. Wet Assays or Analyses. 
— Part IV. Labratory Tests on Ores. Assay, Blow¬ 
pipe, and Qualitative Schemes.— Part V. Tables, 
Examples, and References. 

A 

Manual of Practical Assaying. 

By H. VAN F. FURMAN, E.M. 

FIFTH EDITION, REVISED. 

8vo. 475 pages. Cloth, $3.00. 

CONTENTS:— Part I. Introductory.— Part II. Deter¬ 
minations.— Part III. Special Assays and Analyses.— 
Part IV. Calculations. Tables.— Appendices. Ap¬ 

pendix A. Melting and Refining Gold Bullion. Appen¬ 
dix B. The Preparation of Pure Gold and Silver. Ap¬ 
pendix C. Losses of Gold and Silver in the Fire Assay. 
Appendix D. Laboratory Tests in Connection with the 
Extraction of Gold by the Cyanide Process. Appendix 
E The Analysis of Refined Copper. Appendix F. 
The Mechanical Assay of Gold and Silver Ores. 
Appendix G. The Calculation of Copper-matte Blast¬ 
furnace Charges. Index. 




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Barr’s Kinematics of Machinery.8vo, 

* Bartlett’s Mechanical Drawing.8vo, 

Durley’s Elementary Text-book of the Kinematics of Machines. 

(In preparation.) 

Hill’s Text-book on Shades and Shadows, and Perspective.. 8vo, 
Jones’s Machine Design: 

Part I.—Kinematics of Machinery.8vo, 

Part II.—Form, Strength and Proportions of Parts.8vo, 

MacCord’s Elements of Descriptive Geometry.8vo, 

Kinematics; or, Practical Mechanism.8vo, 

Mechanical Drawing.4to, 

Velocity Diagrams.8vo, 

* Mahan’s Descriptive Geometry and Stone-cutting.8vo, 

Mahan’s Industrial Drawing. (Thompson.).8vo, 

Reed’s Topographical Drawing and Sketching.4to, 

Reid’s Course in Mechanical Drawing.8vo, 

Text-book of Mechanical Drawing and Elementary Ma¬ 
chine Design.8vo, 

Robinson’s Principles of Mechanism.8vo, 

Smith’s Manual of Topographical Drawing. (McMillan.) .8vo, 
Warren’s Elements of Plane and Solid Free-hand Geometrical 

Drawing .12mo, 

“ Drafting Instruments and Operations.12mo, 

Manual of Elementary Projection Drawing.... 12mo, 
Manual of Elementary Problems in the Linear Per¬ 
spective of Form and Shadow.12mo, 

“ Plane Problems in Elementary Geometry.12mo, 

Primary Geometry.12mo, 

“ Elements of Descriptive Geometry, Shadows, and Per¬ 
spective .8vo, 

“ General Problems of Shades and Shadows.8vo, 

“ Elements of Machine Construction and Drawing. .8vo, 
“ Problems, Theorems, and Examples in Descriptive 

Geometry.8vo, 

Weisbach’s Kinematics and the Power of Transmission. (Herr¬ 
mann and Klein.).8vo, 

Whelpley’s Practical Instruction in the Art of Letter En¬ 
graving .12mo, 

Wilson’s Topographic Surveying.8vo, 

Wilson’s Free-hand Perspective.8vo, 

Woolf’s Elementary Course in Descriptive Geometry. .Large 8vo, 

9 


2 50 

3 00 


2 00 

1 50 
3 00 

3 00 
5 00 

4 00 
1 50 

1 50 
3 50 

5 00 

2 00 

3 00 
3 00 

2 50 

I 00 
1 25 
1 50 

1 00 

1 25 
75 

3 50 
3 00 
7 50 

2 50 
5 00 

2 00 

3 50 

2 50 

3 00 



































ELECTRICITY AND PHYSICS. 

Anthony and Brackett’s Text-book of Physics. (Magie.) 

Small 8vo, 3 00 

Anthony’s Lecture-notes on the Theory of Electrical Measur- 

ments .12mo, 1 00 

Benjamin’s History of Electricity.8vo, 3 00 

Benjamin’s Voltaic Cell.8vo, 3 00 

Classen’s Qantitative Chemical Analysis by Electrolysis. Her¬ 
rick and Boltwood.).8vo, 3 00 

Crehore and Squier’s Polarizing Photo-chronograph.8vo, 3 00 

Dawson’s Electric Railways and Tramways..Small 4to, half mor., 12 50 
Dawson’s “ Engineering ” and Electric Traction Pocket-book. 

16mo, morocco, 4 00 

Flather’s Dynamometers, and the Measurement of Power. . 12mo, 3 00 

Gilbert’s De Magnete. (Mottelay.).8vo, 2 60 

Holman’s Precision of Measurements.8vo, 2 00 

“ Telescopic Mirror-scale Method, Adjustments, and 

Tests .Large 8vo, 75 

Landauer’s Spectrum Analysis. (Tingle.).8vo, 3 00 

Le Chatelier’s High-temperature Measurements. (Boudouard— 

Burgess.).12mo, 3 00 

Lbb’s Electrolysis and Electrosynthesis of Organic Compounds. 

(Lorenz.) .12mo, 1 00 

Lyons’s Treatise on Electromagnetic Phenomena.8vo, 6 00 

* Michie. Elements of Wave Motion Relating to Sound and 

Light.8vo, 4 00 

Niaudet’s Elementary Treatise on Electric Batteries (Fish- 

back.) .12mo, 2 50 

* Parshall and Hobart’s Electric Generators..Small 4to, half mor., 10 00 

Thurston’s Stationary Steam-engines.8vo, 2 50 

•Tillman. Elementary Lessons in Heat.8vo, 1 50 

Tory and Pitcher. Manual of Laboratory Physics. .Small 8vo, 2 OO 

LAW. 

•Davis. Elements of Law.8vo, 2 50 

* “ Treatise on the Military Law of United States. .8vo, 7 00 

* Sheep, 7 50 

Manual for Courts-martial.16mo, morocco, 1 50 

Wait’s Engineering and Architectural Jurisprudence.8vo, 6 00 

Sheep, 6 50 

“ Law of Operations Preliminary to Construction in En¬ 
gineering and Architecture.8vo, 5 00 

Sheep, 5 60 

“ Law of Contracts.8vo, 3 00 

Winthrop’s Abridgment of Military Law.12mo, 2 50 

MANUFACTURES. 

Beaumont’s Woollen and Worsted Cloth Manufacture. .. .12mo, 1 50 

Bemadou’s Smokeless Powder—Nitro-cellulose and Theory of 

the Cellulose Molecule.l2mo, 2 50 

Bolland’s Iron Founder.12mo, cloth, 2 50 

“The Iron Founder” Supplement.12mo, 2 50 

Encyclopedia of Founding and Dictionary of Foundry 

Terms Used in the Practice of Moulding.... 12mo, 3 00 

Eissler’s Modern High Explosives.8vo, 4 00 

Effront’s Enzymes and their Applications. (Prescott.) {In preparation.) 
Fitzgerald’s Boston Machinist.18mo, 1 00 


10 





























Ford's Boiler Making for Boiler Makers.18mo, 

Hopkins’s Oil-chemists’ Handbook.8vo, 

Keep’s Cast Iron. (In preparation.) 

Metcalf’s Steel. A Manual for Steel-users.12mo, 

Metcalf’s Cost of Manufactures—And the Administration of 

Workshops, Public and Private.8vo, 

Meyer’s Modern Locomotive Construction.4to, 

* Reisig’s Guide to Piece-dyeing.8vo, 

Smith’s Press-working of Metals.8vo, 

“ Wire: Its Use and Manufacture.Small 4to, 

Spalding’s Hydraulic Cement.12mo, 

Spencer’s Handbook for Chemists of Beet-sugar Houses. 

16mo, morocco, 

“ Handbook for Sugar Manufacturers and their Chem¬ 
ists.16mo, morocco, 

Thurston’s Manual of Steam-boilers, their Designs, Construc¬ 
tion and Operation.8vo, 

Walke’s Lectures on Explosives.8vo, 

West’s American Foundry Practice.I2mo, 

“ Moulder’s Text-book.12mo, 

Wiechmann’s Sugar Analysis....Small 8vo, 

Wolff’s Windmill as a Prime Mover.8vo, 

Woodbury’s Fire Protection of Mills.8vo, 


1 00 
3 00 

2 00 

5 00 
10 00 
25 00 
3 00 
3 00 
2 00 

3 00 

2 00 


5 

4 

2 

2 

2 

3 

2 


00 

00 

50 

50 

50 

00 

50 


MATHEMATICS. 


Baker’s Elliptic Functions.8vo, 1 50 

* Bass’s Elements of Differential Calculus.12mo, 4 00 

Briggs’s Elements of Plane Analytic Geometry.12mo, 1 00 

Chapman’s Elementary Course in Theory of Equations... 12mo, 1 50' 

Compton’s Manual of Logarithmic Computations.12mo, 1 50 

Davis’s Introduction to the Logic of Algebra.8vo, 1 50 

Halsted’s Elements of Geometry.8vo, 1 75 

“ Elementary Synthetic Geometry.8vo, 1 50 

Johnson’s Three-place Logarithmic Tables: Vest-pocket size,pap., 15 

100 copies for 5 00 
Mounted on heavy cardboard, 8 X 10 inches, 25 

10 copies for 2 00 

“ Elementary Treatise on the Integral Calculus. 

Small 8vo, 1 50 

“ Curve Tracing in Cartesian Co-ordinates.12mo, 1 00 

“ Treatise on Ordinary and Partial Differential 

Equations.Small 8vo, 3 50' 

“ Theory of Errors and the Method of Least 

Squares .12mo, 1 50 

* “ Theoretical Mechanics.. „ „.. 12mo, 3 00' 

* Ludlow and Bass. Elements of Trigonometry and Logarith¬ 

mic and Other Tables.8vo, 3 

“ Trigonometry. Tables published separately. .Each, 2 

Merriman and Woodward. Higher Mathematics.8vo, 5 

Merriman’s Method of Least Squares.8vo, 2 00‘ 

Rice and Johnson’s Elementary Treatise on the Differential 

Calculus.Small 8vo, 3 00 

“ Differential and Integral Calculus. 2 vols. 

in one.Small 8vo, 2 

Wood’s Elements of Co-ordinate Geometry.8vo, 2 

“ Trigometry: Analytical, Plane, and Spherical.... 12mo, 1 

11 


00 

00 

00 


50 ' 

00 

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MECHANICAL ENGINEERING. 

MATERIALS OF ENGINEERING, STEAM ENGINES 

AND BOILERS. 

Baldwin's Steam Heating for Buildings.12mo, 

Barr’s Kinematics of Machinery.8vo, 

* Bartlett’s Mechanical Drawing.8vo, 

Benjamin’s Wrinkles and Recipes.12mo, 

Carpenter’s Experimental Engineering.8vo, 

Heating and Ventilating Buildings.8vo, 

Clerk’s Gas and Oil Engine.Small 8vo, 

Cromwell’s Treatise on Toothed Gearing.12mo, 

Treatise on Belts and Pulleys.12mo, 

Durley’s Elementary Text-book of the Kinematics of Machines. 

(In preparation.) 

Flather’s Dynamometers, and the Measurement of Power .. 12mo, 

Rope Driving.12mo, 

dill’s Gas an Fuel Analysis for Engineers.12mo, 

Hall’s Car Lubrication.12mo, 

Jones’s Machine Design: 

Part I.—Kinematics of Machinery.8vo, 

Part II.—Form, Strength and Proportions of Parts.8vo, 

Kent’s Mechanical Engineers’ Pocket-book.... 16mo, morocco, 

Kerr’s Power and Power Transmission. (In preparation.) 

MacCord’s Kinematics; or, Practical Mechanism.8vo, 

“ Mechanical Drawing.4to, 

Velocity Diagrams.8vo, 

Mahan’s Industrial Drawing. (Thompson.).8vo, 

Poole’s Calorific Power of Fuels.8vo, 

Reid’s Course in Mechanical Drawing.8vo, 

Text-book of Mechanical Drawing and Elementary 

Machine Design.,.8vo, 

Richards’s Compressed Air.12mo, 

Robinson’s Principles of Mechanism.8vo, 

Smith’s Press-working of Metals.8vo, 

Thurston’s Treatise on Friction and Lost Work in Machin¬ 
ery and Mill Work. 8vo, 

Animal as a Machine and Prime Motor and the 

Laws of Energetics.12mo, 

Warren’s Elements of Machine Construction and Drawing. .8vo, 
Weisbach’s Kinematics and the Power of Transmission. (Herr¬ 
mann—Klein.) .8vo, 

“ Machinery of Transmission and Governors. (Herr¬ 
mann—Klein.) .8vo, 

“ Hydraulics and Hydraulic Motors. (Du Bois.) .8vo, 

Wolff’s Windmill as a Prime Mover.8vo, 

W 7 ood’s Turbines.8vo, 


MATERIALS OF ENGINEERING. 

Bovey's Strength of Materials and Theory of Structures. .8vo, 
Burr’s Elasticity and Resistance of the Materials of Engineer¬ 
ing .8vo, 

'Church’s Mechanics of Engineering.8vo, 

Johnson’s Materials of Construction.Large 8vo, 

"Keep’s Cast Iron. (In preparation.) 

Lanza’s Applied Mechanics.8vo, 

-Martens’s Handbook on Testing Materials. (Henning )... .8vo, 
Merriman’a Text-book on the Mechanics of Materials. .. .8vo, 
“ Strength of Materials.12mo, 


2 50 

2 50 

3 00 
2 00 
6 00 

3 00 

4 00 
1 50 
1 50 


3 00 
2 00 
1 25 
1 00 

1 50 

3 00 
5 00 

5 00 

4 00 

1 50 
3 50 
3 00 

2 00 

3 00 

1 50 
3 00 
3 00 

3 00 

1 00 
7 50 

5 00 

5 00 
5 00 
3 00 

2 50 


7 50 

5 00 

6 00 
6 00 

7 50 
7 50 
4 00 
1 00 





































Metcalf’s Steel. A Manual for Steel-users.12mo, 

Smith’s Wire: Its Use and Manufacture.Small 4to, 

Thurston’s Materials of Engineering.3 vols., 8vo 

Part II.—Iron and Steel. . ...\ 8vo ; 

Part III.-—A Treatise on Brasses, Bronzes and Other Alloys 

and their Constituents...8vo, 

Thurston’s Text-book of the Materials of Construction. ... 8vo, 
Wood’s Treatise on the Resistance of Materials and an Ap¬ 
pendix on the Preservation of Timber.8vo, 

Elements of Analytical Mechanics.8vo, 


STEAM ENGINES AND BOILERS. 

Carnot’s Reflections on the Motive Power of Heat. (Thurston.) 

12mo, 

Dawson’s “ Engineering ” and Electric Traction Pocket-book. 

16mo, morocco, 

Ford’s Boiler Making for Boiler Makers.18mo, 

Hemenway’s Indicator Practice and Steam-engine Economy- 

12mo, 

Hutton’s Mechanical Engineering of Power Plants.8vo, 

Heat and Heat-engines.8vo, 

Kent’s Steam-boiler Economy.8vo, 

Kneass’s Practice and Theory of the Injector.8vo, 

MacCord’s Slide-valves.8vo, 

Meyer’s Modern Locomotive Construction.4to, 

Peabody’s Manual of the Steam-engine Indicator.12mo, 

Tables of the Properties of Saturated Steam and 

Other Vapors.8vo, 

Thermodynamics of the Steam-engine and Other 

Heat-engines.8vo, 

Valve-gears for Steam-engines.Svo, 

Peabody and Miller. Steam-boilers.8vo, 

Pray’s Twenty Years with the Indicator.Large 8vo, 

Pupin’s Thermodynamics of Reversible Cycles in Gases and 

Saturated Vapors. (Osterberg.).12mo, 

Reagan’s Locomotive Mechanism and Engineering.12mo, 

Rontgen’s Principles of Thermodynamics. (Du Bois.). .. .8vo, 
Sinclair’s Locomotive Engine Running and Management. . 12mo, 
Smart’s Handbook of Engineering Laboratory Practice. . 12mo, 

Snow’s Steam-boiler Practice.Svo, 

Spangler’s Valve-gears.Svo, 

“ Notes on Thermodynamics.12mo, 

Thurston’s Handy Tables.Svo, 

“ Manual of the Steam-engine.2 vols., Svo, 

Part I.—History, Structure, and Theory.8vo, 

Part II.—Design, Construction, and Operation.8vo, 

Thurston’s Handbook of Engine and Boiler Trials, and the Use 

of the Indicator and the Prony Brake.8vo, 

“ Stationary Steam-engines.8vo, 

“ Steam-boiler Explosions in Theory and in Prac¬ 
tice .12mo, 

“ Manual of Steam-boilers, Their Designs, Construc¬ 
tion, and Operation.8vo, 

Weisbach’s Heat, Steam, and Steam-engines. (Du Bois.)..Svo, 

WHiitham’s Steam-engine Design.8vo, 

Wilson’s Treatise on Steam-boilers- (Flather-).16mo, 

Wood’s Thermodynamics, Heat Motors, and Refrigerating 
Machines .8vo, 


2 OO 

3 OO 
8 00 
3 50 

2 50 
5 OO 

2 OO 

3 00 


1 50 

4 00 
1 00 

2 00 

5 00 
5 00 

4 00 

1 50 

2 00 
10 00 

1 50 

1 00 

5 00 

2 50 

4 00 
2 50 

1 25 

2 00 

5 00 
2 00 

2 50 

3 00 
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1 00 

1 50 
10 00 

6 00 
6 00 

5 00 

2 50 

1 50 


5 00 
5 00 
5 00 
2 50 

4 00 


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MECHANICS AND MACHINERY. 

Barr’s Kinematics of Machinery.8vo, 2 50 

Bovey’s Strength of Materials and Theory of Structures. .8vo, 7 50 

Chordal.—Extracts from Letters.12mo, 2 00 

Church’s Mechanics of Engineering.8vo, 6 00 

“ Notes and Examples in Mechanics.8vo, 2 00 

Compton’s First Lessons in Metal-working.12mo, 1 50 

Compton and De Groodt. The Speed Lathe.12mo, 160 

Cromwell’s Treatise on Toothed Gearing.12mo, 1 50 

“ Treatise on Belts and Pulleys.12mo, 1 50 

Dana’s Text-book of Elementary Mechanics for the Use of 

Colleges and Schools.12mo, 1 50 

Dingey’s Machinery Pattern Making.12mo, 2 00 

Dredge’s Record of the Transportation Exhibits Building of the 

World’s Columbian Exposition of 1893.4to, half mor., 5 00 

Du Bois’s Elementary Principles of Mechanics: 

Vol. I.—Kinematics.8vo, 3 50 

Vol. II.—Statics.8vo, 4 00 

Yol. III.—Kinetics.8vo, 3 50 

Du Bois’s Mechanics of Engineering. Vol. I.Small 4to, 10 00 

Durley’s Elementary Text-book of the Kinematics of Machines. 

{In preparation.) 

Fitzgerald’s Boston Machinist. 16mo, 

Flather’s Dynamometers, and the Measurement of Power. 12mo, 

“ Rope Driving.12mo, 

Hall’s Car Lubrication.12mo, 

Holly’s Art of Saw Filing.18mo, 

* Johnson’s Theoretical Mechanics.12mo, 

Jones’s Machine Design: 

Part I.—Kinematics of Machinery.8vo, 

Part II.—Form, Strength and Proportions of Parts. .. .8vo, 

Kerr’s Power and Power Transmission. {In preparation.) 

Lanza’s Applied Mechanics.8vo, 

MacCord’s Kinematics; or, Practical Mechanism.8vo, 

“ Velocity Diagrams.8vo, 

Merriman’s Text-book on the Mechanics of Materials.8vo, 

* Michie’s Elements of Analytical Mechanics.8vo, 

Reagan’s Locomotive Mechanism and Engineering.12mo, 

Reid’s Course in Mechanical Drawing.8vo, 

“ Text-book of Mechanical Drawing and Elementary 

Machine Design.8vo, 3 00 

Richards’s Compressed Air.12mo, 1 50 

Robinson’s Principles of Mechanism.8vo, 3 00 

Sinclair’s Locomotive-engine Running and Management.. 12mo, 2 00 

Smith’s Press-working of Metals.8vo, 3 00 

Thurston’s Treatise on Friction and Lost Work in Machin¬ 
ery and Mill Work.8vo, 3 00 

“ Animal as a Machine and Prime Motor, and the 

Laws of Energetics. 12mo, 1 00 

Warren’s Elements of Machine Construction and Drawing. .8vo, 7 50 

Weisbach’s Kinematics and the Power of Transmission. 

(Herrman—Klein.) .8vo, 5 00 

“ Machinery of Transmission and Governors. (Herr- 

(man—Klein.) .8vo, 5 00 

Wood’s Elements of Analytical Mechanics.8vo, 3 00 

" Principles of Elementary Mechanics.12mo, 1 25 

* Turbines .8vo, 2 50 

The World’s Columbian Exposition of 1893.4to, 1 00 

14 


1 

3 

2 

1 


1 

3 

7 

5 

1 

4 
4 
2 
2 


00 

00 

00 

00 

75 

00 

50 

00 

50 

00 

50 

00 

00 

00 

00 










































METALLURGY. 


Egleston’s Metallurgy of Silver, Gold, and Mercury: 

Vol. I—Silver.8vo, 7 50 

Vol. II.—Gold and Mercury.8vo, 7 50 

Keep’s Cast Iron. (In preparation.) 

Kunhardt’s Practice of Ore Dressing in Europe.8vo, 1 50 

Le Chatelier’s High-temperature Measurements. (Boudouard— 

Burgess.) .12mo, 3 00 

Metcalfs Steel. A Manual for Steel-users.12mo, 2 00 

Thurston’s Materials of Engineering. In Three Parts.8vo, 8 00 

Part II.—Iron and Steel.8vo, 3 50 

Part III.—A Treatise on Brasses, Bronzes and Other Alloys 

and Their Constituents.8vo, 2 50 


MINERALOGY. 

Barringer’s Description of Minerals of Commercial Value. 

Oblong, morocco, 2 50 

Boyd’s Resources of Southwest Virginia.8vo, 3 00 

“ Map of Southwest Virginia.Pocket-book form, 2 00 

Brush’s Manual of Determinative Mineralogy. (Penfield.) .8vo, 4 00 

Chester’s Catalogue of Minerals.8vo, paper, 1 00 

Cloth, 1 25 

“ Dictionary of the Names of Minerals.8vo, 3 50 

Dana’s System of Mineralogy.Large 8vo, half leather, 12 50 

" First Appendix to Dana’s New “ System of Mineralogy.” 

Large 8vo, 1 00 

“ Text-book of Mineralogy.8vo, 4 00 

Minerals and How to Study Them.12mo, 1 50 

“ Catalogue of American Localities of Minerals. Large 8vo, 1 00 

“ Manual of Mineralogy and Petrography.12mo, 2 00 

Egleston’s Catalogue of Minerals and Synonyms.8vo, 2 50 

Hussak’s The Determination of Rock-forming Minerals. 

(Smith.) .Small 8vo, 2 00 

* Penfield’s Notes on Determinative Mineralogy and Record of 

Mineral Tests.8vo, paper, 50 

Rosenbusch’s Microscopical Physiography of the Rock-making 

Minerals. (Idding’s.).8vo, 5 00 

•Tillman’s Text-book of Important Minerals and Rocks. .8vo, 2 00 
Williams’s Manual of Lithology.8vo, 3 00 


MINING. 

Beard’s Ventilation of Mines.12mo, 2 50 

Boyd’s Resources of Southwest Virginia.8vo, 3 00 

“ Map of Southwest Virginia.Pocket-book form, 2 00 

* Drinker’s Tunneling, Explosive Compounds, and Rock 

Drills.4to, half morocco, 25 00 

EissleFs Modern High Explosives.8vo, 4 00 

Goodyear’s Coal-mines of the Western Coast of the United 

States .12mo, 2 

Ihlseng’s Manual of Mining.8vo, 4 

Kunhardt’s Practice of Ore Dressing in Europe.8vo, 1 

O’Driscoll’s Notes on the Treatment of Gold Ores.8vo, 2 

Sawyer’s Accidents in Mines.8vo, 7 

Walke’s Lectures on Explosives.8vo, 4 

Wilson’s Cyanide Processes.12mo, 1 

Wilson’s Chlorination Process.12mo, 1 


50 

00 

60 

00 

00 

00 

50 

60 


15 




































Wilson’s Hydraulic and Placer Mining.12mo, 

Wilson’s Treatise on Practical and Theoretical Mine Ventila¬ 
tion .12mo, 


SANITARY SCIENCE. 

Folwell’s Sewerage. (Designing, Construction and Maintenance.) 

8vo, 

“ Water-supply Engineering.8vo, 

Fuertes’s Water and Public Health.12mo, 

u Water-filtration Works.12mo, 

Gerhard’s Guide to Sanitary House-inspection.16mo, 

Goodrich’s Economical Disposal of Towns’ Refuse... Demy 8vo, 

Hazen’s Filtration of Public Water-supplies.8vo, 

Kiersted’s Sewage Disposal.12mo, 

Mason’s Water-supply. (Considered Principally from a San¬ 
itary Standpoint.8vo, 

“ Examination of Water. (Chemical and Bacterio¬ 
logical.) .12mo, 

Merriman’s Elements of Sanitary Engineering.8vo, 

Nichols’s Water-supply. (Considered Mainly from a Chemical 

and Sanitary Standpoint.) (1883.) .8vo, 

Ogden’s Sewer Design.12mo, 

Richards’s Cost of Food. A Study in Dietaries.12mo, 

Richards and Woodman’s Air, Water, and Food from a Sani¬ 
tary Standpoint.8 vo, 

Richards’s Cost of Living as Modified by Sanitary Science. 12mo, 

Rideal’s Sewage and Bacterial Purification of Sewage.8vo, 

Turneaure and Russell’s Public Water-supplies.8vo, 

Whipple’s Microscopy of Drinking-water._.8vo, 

Woodhull’s Notes on Military Hygiene.16mo, 

MISCELLANEOUS. 

Barker’s Deep-sea Soundings.8vo, 

Emmons’s Geological Guide-book of the Rocky Mountain Ex¬ 
cursion of the International Congress of Geologists. 

Large 8vo, 

Ferrel’s Popular Treatise on the Winds.8vo, 

Haines’s American Railway Management.12mo, 

Mott’s Composition, Digestibility, and Nutritive Value of Food. 

Mounted chart, 

Fallacy of the Present Theory of Sound.16mo, 

Ricketts’s History of Rensselaer Polytechnic Institute, 1824- 

1894.Small 8vo, 

Rotherham’s Emphasised New Testament.Large 8vo, 

Critical Emphasised New Testament.12mo, 

Steel’s Treatise on the Diseases of the Dog.8vo, 

Totten’s Important Question in Metrology.8vo, 

The World’s Columbian Exposition of 1893.4to, 

Worcester and Atkinson. Small Hospitals, Establishment and 
Maintenance, and Suggestions for Hospital Architecture, 
with Plans for a Small Hospital. .12mo, 

HEBREW AND CHALDEE TEXT-BOOKS. 

Green’s Grammar of the Hebrew Language.8vo, 

Elementary Hebrew Grammar.12mo, 

Hebrew Chrestomathy.8vo, 

Gesenius’s Hebrew and Chaldee Lexicon to the Old Testament 

Scriptures. (Tregelles.).Small 4to, half morocco, 

Letteris’s Hebrew Bible.8vo, 

16 


2 00 

1 25 


3 00 

4 00 

1 50 

2 50 
1 00 

3 50 
3 00 
1 25 

5 00 

1 25 

2 00 

2 50 
2 00 
1 00 

2 00 
1 00 

3 50 
5 00 
3 50 
1 50 


2 00 


1 50 
4 00 

2 50 

1 25 
1 00 

3 00 

2 00 

1 50 
3 50 

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1 00 


1 25 


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2 25 













































MAR 26 1902 

WAR. 26 1902 
' p . 3 ! 






































